P-47 Thunderbolt Pt. 2 Dive Speeds and Mach Numbers

[@borisspleit7105]

I had an honor to be taught by a Russian colonel who was a head of chair for aerodynamics in Moscow and whose son is a pilot...he told us how his son asked him ( a long time after becoming a pilot ) something this man thought every pilot should know...and he told his son that the pilots are like the bears driving a bicycle in circus - they know how to fly but they don't know how. That can't be said about You,Greg. Nice work.

[@christopherchartier3017]

That’s definitely sounds like something a Russian Colonel would say

[@lylepetrick3165]

Thank you, my 7 year old has taken a fascination with history and airplanes. We have been watching these videos together they are excellent. Keep them coming

[@GregsAirplanesandAutomobiles]

Wow, if your 7 year old can understand these, that's one bright kid.

[@paulmanson253]

Now that was just plain interesting. Smoky Yunick was a Flying Sergeant during WWII. In several of his articles and at least one of his publications (Smoky Yunick's Power Secrets) he had extremely high praise for what he called the Stromberg pressure carburetor and stated that it was his inspiration for the concept he called a "fueler" fuel supply device irrespective of design. So I always wondered just what the heck this mythical wonder critter was. And now I know. So thanks for that. This article brought back a memory. Early 70s,I think it was Private Pilot magazine,a man who had been trained by a Navy old timer himself reminisced that he was told there was extreme reluctance on the part of the Navy pilots to transition to monoplane fighters. The phrase he used was that the performance envelope was entirely within the design envelope. The sturdy late 30s Navy biplanes could safely go into a vertical dive,full power,and the resistance of two wings and associated flying wires etc would guarantee full controllabilty by the pilot,and reliable terminal velocity. And with experience, they trained to land their beasts on a marked spot of the carrier deck without need of the arresting hook. Try that with an F14. Different design envelope indeed. So thanks again for a very good reason to keep looking at KZbin. Cheers.

[@Completeaerogeek]

Hi Greg I have run these numbers myself and it is interesting to note the 'warning'; in the RAE tests about lack of elevator authority and the necessity to use the trim wheel to recover, not something a combat pilot may remember hence the trouble some P-47 pilots got into. Also I have charts from the RAE showing tests flown by Jeffrey Quill with a Mach number comparison (with a P-51) of the Spitfire at 0.89. The size of the blisters over the cannon apparently had some effect. The PR models had a higher MCrit. Later aircraft had smaller blisters and so a higher MCrit. And we also have the 1944 RAE tests flown by SQNLDR Tony Martindale in excess of Mach 0.90. Only the overspeeding propeller and reduction gearbox failure caused trouble when they departed the aircraft and an 11G recovery wrinkled the aircraft quite a bit.. Even then, he recovered and landed the aircraft, recording devices intact.

[@GregsAirplanesandAutomobiles]

Trim is a factor, but I don't know of a single WW2 era airplane where it wasn't a factor in recovering from a high speed dive. The P-47 isn't special in that regard. I have read these stories of Spitfires reaching .89 and .90, but what I can't find is a single picture anywhere of a Spitfire with equipment for measuring mach number mounted on it. If you can point me to such a picture, I would love to see it. We can find these for the P-47, as well as other U.S. aircraft, one is the thumbnail for this video.

[@Completeaerogeek]

Elevator authority in a dive at high speed, Trim and Mach tuck was quite variable between aircraft, the P-38 being a particularly severe example of a dive-/Mach limited aircraft, as you noted in your video on it. The amount of remaining elevator authority or where trim only could effect recovery as the elevators were immovable by the pilot, seems to have been a feature of the P-47 at high dive speed at altitude, hence the warning to pilots. BTW, I am still looking for a pic of the calibrated trace recorders used by the RAF AFDU and Aerodynamics Flight at Farnborough during these tests.(It is clear they used them from the specificity of the data) I have a request in with the RAF Museum to see if they can help.

[@steveshoemaker6347]

Well done , I like flying the 104's but the p-47 is my dream,to old now 78 years gone by ....Thanks very much !

[@jeromestern8225]

The best channel regarding the understanding of ww2 planes I've come across. Thanks

[@rayschoch5882]

Once again, an excellent explanation that a non-engineer can understand. My dad was a WW II pilot (F6F, F4U4), then a test pilot for McDonnell (F1H, F2H, XF-85, XF-88), and I wanted to be a pilot, too, but gave up on aviation as a career when I realized I didn't (and still don't) understand "higher" math. I can do arithmetic as well as anyone, and understand ratios and relationships, but was convinced I needed to be able to do calculus and trigonometry, which never happened. Too bad that last little bit about math in your video wasn't available to me in 1956 (6th grade) to provide some encouragement.

[@GregsAirplanesandAutomobiles]

Hi Ray, thanks for your kind words.

[@chucksmith6749]

One only needs basic math to be a good pilot....professional or recreation flying. Now a days computers run all advanced systems. Though it's always important to know how to fly manually if all the bells and whistles fail. The mathematics does not take a rocket scientist to figure out. If it did, most pilots couldn't do it or have just a vague understanding of. Now, test flying is different and requires engineering knowledge. But, that's ok. Basic algebra is usually enough. Don't let math knowledge stop you from reaching your flying goals....if I can do it(and have) then you can do it too... PMA...positive mental attitude....

[@Gronicle1]

Still have my circular slide rule from early 1970's. Used it on the boats to work drift and other navigation problems, etc. Great little tool and no batteries to fail when things are getting squeaky!

[@stevekirkham5193]

And your slide rule could survive being dropped and stepped on.

[@mizaru5413]

I had two, a 4" and an 8".

[@radioguy1620]

Better hang onto it , might be outlawed someday, google wont be able to tell what you are doing

[@texhaines9957]

Yes I have one & my Dad's K&E. Great tools.

[@ditto1958]

I remember when I was a kid and my friend was in ground school He showed me his “computer” and tried to teach me how to use it I flunked- couldn’t figure that thing out to save my life It was as if an evil math teacher decided to make a slide rule that would give me nightmares for life 🙂

[@Anotherway04]

Another outstanding and informative WW II airplane video. The pilots back then had to be and were very smart, courageous and capable in many ways. Using the basics @15:18 for the Bonus Round @ 19:50 : For temperature conversion (C x 1.8) + 32= F. For temperature range C x 1.8= F. A 70 C degree temp. range = 126 F temp. range. The Mach range for the given temp. range (15C to --55C) is 87 knots or 100.05 mph. Knots. x 1.15= mph. This translates into a Mach speed decrease of .794 mph per 1 F temp. decrease = 100.05\126= .794. 59 F - 10 F (temp. @25k ft.)= 49 F. 49 x .794= 38.9 mph. Mach at 59 F (15 C)= 760.15 mph. 760.15 - 38.9= 721.25 mph. 540\721.25= Mach .748

[@GregsAirplanesandAutomobiles]

Well done.

[@Anotherway04]

@@GregsAirplanesandAutomobiles Thanks very much. It took some effort to figure and reason out the problem and factors there in. In addition, the very fined tuned and precise analog charts and grafts used in your videos are quite impressive and likewise challenging. WW II Army Air Corp. personnel were very skilled and competent in so many ways and respects.

[@kellerbrooks6430]

Being an graduate engineer from many, many decades ago, I appreciate a good tech video. Keep them coming!

[@billtimmons7071]

Excluding the later model P-38, it amazes me that these aircraft had manual non-boosted controls and were able to manage the compressible effects at all. It must have been very fatiguing to fly combat with these aircraft especially when diving away from danger. Another great video that serves us aviation nerds. Thank you.

[@billtimmons7071]

@@w8stral Try pulling up on the elevator when the elevator is "locked" due to a shock wave. Aerodynamic forces get multiplied so I'm not sure how knowing numbers helps the pilots physical workload. I dont buy your statement.

[@billtimmons7071]

​@@w8stral OK ... we're on different flight paths. You said - "No amount of Brawn will get you past critical mach. " ???? Are you saying diving a heavy aircraft will never get you to critical mach? It does't take brawn to dive an aircraft does it? You will dive to live correct? Are you saying that in dog fight the pilot is always ... just memorizing numbers? Why have aircraft lost their maneuverability (and control surfaces) during high speed combat ... or why did the Zero's ailerons get un- responsive during high speed combat? Zero pilots simply couldn't move the ailerons as effective at higher speeds. USN figured it out and killed Zeros because of it. Why did the MiG -15 (not all controls boosted) lose maneuverability verses the F 86 (boosted all surfaces) while flying at the same high air-speeds? MiG pilots simply couldn't move their controls as effectively. Aircraft controls - non boosted - get "heavier the faster you fly .. it's basic physics. Compressibility makes control surfaces harder to move - that's all the point I was making. The WW2 pilots had a complicated job ... not as easy as you make it sound.

[@billtimmons7071]

@@w8stral bless your heart. "Book" knowledge and some good technical background tends to win the day ... and some wars. Have a good new year.

[@billtimmons7071]

@@w8stral I like our discussion. You have some points. Over the years I've read a great deal, and have amassed a large library of technical/ engineering aviation material. My interest is flight controls from the early manual wing warping to modern fly by wire. Maybe we are both correct? Pilots fly by numbers and they fly by "feel"? Some aircraft have "heavy" controls and others can be flown using the tips of their fingers on the control yoke/stick. Some WW 2 controls got so "heavy" that later models used hydraulic boosted controls, such as the p-38. WW 2 aircraft rarely used hydraulic boost but some did have other boosting such as spring tabs and balance tabs to alleviate control loads as aircraft got faster. I concede your point that in general pilots avoided flight envelopes where they couldn't effectively deflect control surfaces ... but I still say that during combat pilots did what they could to survive. There was a reason designers started boosting controls during WW 2. Thanks for taking time with me. I love aviation, and discussions about aviation. Can we call this draw?

[@BikingVikingHH]

bill Timmons; Whoever is the classiest gentleman to suggest a draw wins the match, automatically. You cannot decline a win good sir. I will not let you.

[@mickvonbornemann3824]

A famous test pilot found that the P47 had compressibility issues at altitude at Mach .7 & was personally thanked by Doolittle. This is what led to the P51 getting the exclusive job of high altitude escort as it more than matched the the BF109 & FW190 mach limits at altitude, which was Mach .75

[@jacktattis]

Dont tell Greg he does not believe those tests

[@kenneth9874]

He was wrong, the raf proved it, the p51 was chosen because of cost efficiency

[@kenneth9874]

@@jacktattis the raf didn't believe him either

[@jacktattis]

@@kenneth9874 No the P51 was chosen first because of the compressibility problems with the P38/ P47

[@jacktattis]

@@kenneth9874 The RAF have nothing to do with Greg

[@jackthompson4993]

Greg- I appreciate your comments on math for pilots. I spent 50 years as both as a private pilot and high-level mechanical engineer. While there are certainly jobs in which engineers may need exotic math skills, much of engineering is similar to flying in that the math has been built into software tools, and the engineer needs to understand relationships and causal factors much more than having to do the math. Many great prospects for engineering careers have been deterred from engineering by math anxiety. I personally feel that skill at 3D visualization and communication is much more important than calculus for most working engineers, yet 4 semesters of calculus are usually required in engineering school curriculums.

[@GregsAirplanesandAutomobiles]

Thanks Jack, that's some great insight.

[@FargoFX]

Brilliant! You answered sooo many questions I’ve had for years. Thank you.

[@steffen19k]

Thank you for your research Greg. Every video you've done on the WW2 warbirds has been phenomenal. I'm looking forward to part 3. I wish more of these videos on youtube were like yours.

[@GregsAirplanesandAutomobiles]

Thanks, I hope to get Part 3 up this week. I am excited about it, it's a fun one to make.

[@MilitaryAviationHistory]

Enjoyed this, very well done. Also, you gave me a good chuckle early on with 'that' Merlin carburetor reference.

[@GregsAirplanesandAutomobiles]

Wow, a celebrity visited my channel. I am honored. You are doing fantastic work over there.

[@SheriffsSimShack]

@@GregsAirplanesandAutomobiles the fatal flaw ;)

[@bradmiller9507]

P-D ...

[@GregsAirplanesandAutomobiles]

I don't have Grand Cherokee, and I am a flight engineer, not a mechanical engineer, which is completely different.

[@danmallery9142]

Thank goodness for Miss Schilling's orifice! :-)

[@HuehuehueWolooo]

You're my favourite channel Greg. And the Jug is my guilty pleasure.

[@laertesl4324]

"Back to normal airplanes" lol. Great video again Greg, thanks.

[@alexzander1839]

Greg thanks for posting and for the benefit of us viewers, I'd love to see you do a complete video on pressure carburetors seen at 1:29-2:29.

[@notaire2]

Very intelligible explanation of the dive speeds and Mach numbers of this flying heavy tank based on the reliable data and precise technological analysis. Simply excellent!

[@hyrumsolo3203]

Hey Greg, I really love your videos and learn so much from them. I hope you someday make a series on the Fw 190!

[@GregsAirplanesandAutomobiles]

Thanks! I am making an FW190 series next.

[@thormod1248]

To mirror your comments about how being a pilot is not as mathematically challenging as it seems before you do it - 100000%. I started flight lessons as a kid way back in the late 90s, and immediately realized that my worries about mathematics and flight were MASSIVELY overblown. As a matter of fact, I had used being a pilot to help keep myself motivated in math classes - until I started learning, and realized how much easier it was than I feared, and for me, how much more "natural" the math for flying worked. You learn to do most common conversions off the top of your head for the aircraft you fly frequently, and it really does become second nature. I dont have to think about what my GS is for an IAS, I just... know because of the aircraft, altitude, conditions, and IAS. And that E6B is so awesome, I still have one in the flight bag for backup right next to the GATS jar. Never rely solely on electronic aids!

[@GregsAirplanesandAutomobiles]

Yup, I think the school system does some real harm by scaring kids away from math. Real math in the real world isn't that hard, it's nothing like in math class.

[@cgoodm]

Another fantastic video Greg, I'm really learning a lot from these. Thank you for making them!

[@tomwaltermayer2702]

Greg, just used this vid to get a student studying for his private written up to speed on speeds. You carried the day where Jepp faltered.

[@GregsAirplanesandAutomobiles]

Wow, I'm glad to hear I could help.

[@bobdyer422]

The "B" model had the fabric covered tail rudders, and elevators all "B" models stayed in the U.S. The"C", "D", and "M" were used in the ETO and MTO. "M" version only used by the 56th F.G. 61st, 62nd and 63rd FS. The "D" and "N" served in the PTO. So far from what I've read "Structure Failure" was only listed in FG's that used the P-51. Col. Hubert Zemke{ former commander of the 56th F.G.} became a POW after his 51 lost it's wings in severe turbulence. The problem became so concerning in the PTO that a B-29 was used to help 51 FG's find their way around weather fronts until they found the Bomber groups the Mustangs were to escort to Japan. The 47 groups had no such trouble. Flying Mustangs over the "Hump" was so dangerous the practice was stopped. Thank you for producing such a thorough and concise production. Always a pleasure! Part three?! NICE!

[@bobparker9511]

This may sound a bit silly but when Greg says "we are going to go into this in great deal" I get a little exited.

[@zunzun9849]

Awesome. Thank you very much for such a clear and informative video. P-47 is my favourite plane in ww2. Looking forward for part 3.

[@tomakers8652]

Greg, your videos are the best. I'm currently building a Top Flite 60" wingspan P-47D RC model and I was very happy to see your P-47 videos. Keep it coming - I thought I knew a lot about WW2 aircraft until I found your channel.

[@GregsAirplanesandAutomobiles]

That sound like a very exciting kit. I just watched your video,the flaps and gear look great.

[@KB4QAA]

Minor points: Jets typically have a Mach Limit speed. Prop/Turboprop aircraft have a MMO, Maximum Mach Operating speed. As jets came into use a more compact circular slide rule was developed known as the "CR" series. The CR2 is small enough to fit military flight suit shoulder pockets. CR3, and CR4 are larger versions.

[@ajgoetsch]

A great job explaining all the principles here and how they relate. Well done and thank you!

[@petersouthernboy6327]

The dive speed, the combat durability, and the heavy armament load made it an ideal ground attack platform

[@GregsAirplanesandAutomobiles]

True, which is ironic since it was designed at a high altitude fighter, literally the opposite of a ground attack plane.

[@hoatattis7283]

Peter : They lost more in that role than any P51 A36 or RAF Mustang or Typhoon

[@hoatattis7283]

peter Southern Boy: And yet it lost 2400+ in that role Source Eric Brown Testing For Combat

[@kenneth9874]

@@hoatattis7283 ho, that's because they did far more of it, however, the loss rate per mission was the lowest of the aforementioned aircraft therefore making it the safest

[@jacktattis]

@@kenneth9874 Not so increasingly the P47 was being replaced by the P51 It was not all at once but little by little the F/Gs were replacing the P47 One group that was not touched was the 56th F/G

[@josephstabile9154]

Great video, in which you go toe to toe to "Winkle" Brown, and his assessment of p-38 & P-47 fighters' deficiencies in Europe, compared with Spitfire, suggesting it was the Luftwaffe's, and especially the Spitfires superior mach numbers! A small correction: you said the chart shows Spitfire Mk IX & Mk XVI, but chart states Mk IX (Merlin) & Mk XIV (Griffon).

[@edwardmonsariste4050]

My grandmother was a Rosie The Riveter that worked on the tail section at the plant in Evansville, Indiana during the war. My grandfather and her married before he was shipped off. She went to work at the plant right after until the end of the war.

[@scarecrow1323]

thank you Greg... fantasticly well done. the technical information you provide is so engaging. 👍👍

[@andreasnilsson2304]

In awe over here.. regarding all the research and "archaeology" you have put in to revealing all the engineering and development that went in to the "old jug". Hats off and deep bow to you Sir.

[@gardenislandlimited1372]

Great work. Very much enjoy these technical details,...keep it up Greg

[@jakobole]

The amount of research that has gone in to this is staggering - fantastic job an quality. This is why we have youtube!

[@stenduginski2306]

Really happy to see another video up, they're always fantastic! Great work again Greg.

[@captaingyro3912]

Minor point, but at 2:45 it says the airspeed indicator is at position 3. The lines are somewhat difficult to follow, but the airspeed indicator is the larger instrument at position 2. It can't be read in this photo, but other photos and cockpit diagrams show the legend on it to be "MPH". The instrument at position 3 is the clock.

[@skylordbob3237]

Again a great video full of interesting stuff about P-47 ! Thx for upload Greg. Can´t wait for part 3! ;D

[@GregsAirplanesandAutomobiles]

Thanks Skylord.I enjoyed the P47 walk around video on your channel. kzbin.info/www/bejne/lZTbeqWtlKp9q8k

[@jonathanrigley981]

Your channel is absolutely fantastic!

[@PeteSampson-qu7qb]

Robert S. Johnson said it very simply. "No enemy pilot tried to escape a Thunderbolt, by diving, twice".

[@BilgePump]

I was going to ask about reaching mach1 in a dive and Greg addressed it. Interesting.

[@hoatattis7283]

Sundance Kid: Not one plane did. But Sqn Leader Tony Martindale ARDU in a Spitfire MkXI reached Mach 0.92 The fastest recorded in WW2 Source Eric Brown Wings on my Sleeve pg 74 The Brits were the only ones that had Mach Metres.

[@jacktattis]

@@hoatattis7283 Meters

[@ctmiljohnson]

Greg, Excellent as usual, especially about my favorite aircraft, keep them coming! Two things: 1. I was under the impression that the dive recovery flaps on the P-47 (and P-38) were placed along the bottom of the wing in a very specific location (about 1/3 back along the cord line) in order to counter the rearward movement of the center of pressure as the aircraft approaches critical Mach. Thus, they don't act so much as speed brakes but rather move the center of pressure forward which provides an "automatic" pitch up moment to help recover from the dive. Is that correct? 2. In regards to the F6F Hellcat's calibrated airspeed being atypically lower than its indicated airspeed, I was reminded of a story I read in the book "Flight Journal" by Corky Meyer. As a Grumman test pilot, Corkey recounts how he flew in formation with a Corsair at high speed and even though the speeds were matched, the Corsair indicated a much higher speed than the Hellcat (15-20 kts?). Corkey then "adjusted" the Hellcat's airspeed indicator to match the Corsair's. This was done in response to the Navy complaining about the slower speed of the Hellcat. This is probably not the reason for the indicated/calibrated anomaly but interesting nonetheless. If you haven't picked it up it's a fantastic book, I highly recommend it. Keep up the good work!

[@GregsAirplanesandAutomobiles]

Hi Chris, good points, both of them. 1. Yes, the dive recovery flaps cause a pitch up moment. They also act as speed brakes, so they help in two ways. I just can't fit everything into these videos, and so few P-47's had them I just didn't spent a lot of time on them. Here is a quote from the manual "The increased diving moment, which would ordinarily result from rearward movement of the center of pressure on the wing when compressibility shock occurs in the dive, is more than offset by the dive-flap action". So yes, they help pitch up. 2. There was a lot more to that story, and in my opinion it relates to marketing by Grumman. The Corsair was faster than the Hellcat according to literally everyone except Grumman. I'll cover this story when I get back to Naval fighters.

[@Spectre407]

Greg's Airplanes and Automobiles - I’ve read the reference he’s talking about. I’m anxious to hear your response regarding Grumman

[@cfsmith3374]

Greg, some V1710 history/folklore. Off topic, but as you've mentioned the Allison V1710 on this channel, I wanted to relay some "history" that might inform a later video. I joined Allison as an engineer in 1986 and was aware of the P51/Packard Merlin history. I asked some the (then) old-timers about this and got the story that follows. These guys were WWII vets, but their careers at Allison did not go back to pre-war days of V1710 development. This is what they heard from earlier engineers, so my version is second hand at best. Allison realized that there were problems installing a turbocharged V1710 in a fighter aircraft and lobbied the Air Force (then USAAC) to fund the development of a 2-stage supercharger for the V1710. GE (who developed turbocharger technology) learned of this and lobbied hard against it. As a result, the project wasn't funded. Further, GE didn't properly support the integration of its turbocharger with the V1710, adding to the development difficulties. Anyway, that's the story these guys told, and this history generated some bad blood. They really hated GE. This sourcing is pretty thin, but it sounds plausible. Allison wouldn't develop a 2-stage super-charger on their own nickel. It would have no commercial application unless you want to pressurize the plane or put all the passengers on oxygen. Since the Navy wasn't interested in liquid-cooled engines, the Air Force was the only customer. If they weren't interested, it wasn't going to be developed. If Allison sought such funding, GE would surely oppose with all their technical and political resources. This happens all the time in the defense contracting world (e.g. the political fight surrounding the F35 alternate engine program). From GE's point of view, it makes sense. Development dollars are always scarce, especially in the late 30's, and they would naturally feel that all available resources should go to their superior (as they undoubtedly saw it) technology. GE would also be inclined to give the V1710 low priority. The USAAC was focused on bombers at the time and gave fighters a very low priority, so a contractor is going to align themselves to the customer's priorities. And any engine maker is going to favor a 4-engine aircraft over a single engine aircraft when it comes to doling out scarce manpower and hardware.

[@GregsAirplanesandAutomobiles]

Hi CF, thanks for sharing. I consider that story to be highly credible. It makes perfect sense and fits all of the known fact perfectly.

[@janlabij7302]

@@GregsAirplanesandAutomobiles - I worked for a development engineer who worked at Allison during WW II. We discussed the V-1710 problems and he talked about crankshaft reliability problems hampering engine reliability above 1350 hp. I must have looked at him funny, because he clarified that the crankshaft was the symptom, the real problem was the crankcase/engine block was flexing (twisting) from the higher torque that higher engine output required.

[@keithstudly6071]

My uncle was in the test area at Allison and the subject hit a nerve with him. His opinion was that development work on the fuel and intake system was all it lacked to being a world beater and somehow that just never got funded. Of course the experience the squadrons had when when Lindbergh flew with them in the Pacific indicated they really had little understanding on how to operate a tubrocharged intercooled engine and were running too rich and too cold and the fuel was condensing in the intercoolers and running in rivlets through the intake manifold with some cylinders getting too much fuel and fowling plugs while other cylinders were running lean and getting detonation damage. Lindbergh showed them how to lean the engines and control the intercooler, (Close the flaps to get a better intake temp.) and the pilots saw improved reliability and were able to add 140 miles to their combat radius. MacArthur heard about this and gave Lindbergh (a civilian) his own P-38 to fly while he was in his command area. A fight between GE and Allison may have been the reason it took so long to understand and adapt to the problems the turbo version of the engine had for sure.

[@AB-re6re]

I'm epileptic and, couldn't get a, private pilots license and, built many scale plastic Kit's as a, kid....& Was impressed with the, P-47 1/32nd. Model and, didn't know how great it was .. thanks again. ..

[@jimattrill8933]

I find all this very interesting. But I wonder if you, Greg, have not heard of Captain Eric Brown RN (recently deceased) who was an amazing test pilot of just about every military aircraft made during world war two and after. While he was at Farnborough he and others were asked by the USAAC General Doolittle to investigate crashes caused by escort fighters crashing after diving from altitude. What was wanted was "hands-on series of tests on three USAAC escort fighters - the P38H Lightning, the P47C Thunderbolt and P51B Mustang. The requirement was for a detailed description of the handling behaviour of these aircraft at high speeds up to their tactical (manouvering) and critical (loss of control) Mach numbers, so that the operational pilots could recognise they were near these limits without reference to the instruments in the cockpit. These tests were initiated in late January 1944 and continued through to early March. It must be remembered that Mach meters were not fitted to any Allied or enemy operational aircraft, but only to a few research aircraft. We knew from tests at RAE on captured German fighters that the Me109 and Fw190 both had a tactical Mach number of 0.75, so that figure was the name of the game at 30 000 ft. The tests we conducted on the American fighters revealed that the Lightning and Thunderbolt fell well short of that figure with tactical Mach numbers of 0.68 and 0.71 respectively. However, the Mustang with its laminar-flow wing achieved 0.78 tactically, and soon after receiving these results Doolittle asked that his Force be supplied with only P-51s. [..] We took a Spitfire XI, a photo-reconnaissance and stripped it of all operational equipment, so that even with the boffin's recording gear aboard it was well below its normal weight. Our Spitfire would go up to 40 000 feet. Up there we would fly it flat out before pushing it over into a steep dive. You would hold onto this screaming plunge until the Machmeter read 0.83. Then a gentle shaking started [...] The dive angle steepened rapidly and the Spitfire started shaking really badly and rolling from side to side. At 0.86 the pilot had to pull the equivalent of 60lb to stop the dive steepening any further. [...] This was my physical limit. Even with both hands I could not pull more than that on the Spitfire's stick. Our flight commander, Squadron Leader Tony Martindale, was a big, powerful six footer. One day he dived to 0.92 at which point he was pulling about 100lb on the control column to recover, when the over-speeding propellor became detached, together with its reduction gear. The resultant loss of weight at the front made the Spitfire tail-heavy and it zoomed almost vertically upwards, blacking out the pilot with a force of 11g. When he recovered his sight again he found himself back up at about 40 000 ft with his straight-winged aircraft having developed a very slightly swept-back look. It speaks volumes for the pilot and the Spitfire that Marty somehow managed to land it back at Farnborough on its wheels, with the valuable camera records intact. The speed he reached in that dive is still the highest ever recorded by a piston-engined aircraft." From "Wings on my sleeve" by Captain Eric Brown CBE, DSC, AFC, MA, Hon FRAeS, RN

[@GregsAirplanesandAutomobiles]

Yes, I have heard of him. However I don't value his observations above NACA's or the US test pilots. Saying the P-47 could only reach mach .71 is just ridiculous. If that was the case Europe would have been littered with P-47 that went into lawn dart mode because the published numbers right on the cockpit placard are much higher than that. Furthermore, every WW2 pilot that I have seen comment on P-47 dive performance has said that it would easily out dive a 109 or 190, and they do .75 or possibly better in some cases. In other words, there is zero corroborating evidence that the P-47 was limited to .71, and a ton of evidence that it could do .80 or better. Regarding the Spitfire, it could reach a high mach number as I explained in my video, however it's airspeed limitations hurt it's overall dive performance. As for the numbers like .92, those are basically B.S. propaganda numbers. Taking a specially prepared plane and running it to the point where it literally falls apart isn't quite the same as a test using a production combat ready plane and getting repeatable results with it that pilots going into combat can duplicate.

[@KennyMarkusa]

@@GregsAirplanesandAutomobiles Quote from Lt.Karl-Heinz Ossenkop Fw-190D pilot JG26 " never try to out dive a Thunderbolt they can dive like a bullet"

[@emersoncaicedo3146]

My man!!! These videos give me life!

[@GregsAirplanesandAutomobiles]

Thanks, I am working on Pt. 3 right now.

[@estern001]

Thank you so much. You talk numbers and I see aircraft in a particular situation. I love imagining the machine on the edge of performance parameters. I imagine a skilled pilot making every possible use of the aircraft. In never thought of this while pulling a Martin-Baker ejection seat out of an F-14 at NAS Miramar in 1986. Go VF-21 Freelancers! USS Constellation!

[@localbod]

Thankyou for another fascinating and informative presentation.

[@bradmiller9507]

Thanks Greg... Keep it Real! Trust that Warm Fuzzy Feeling& You will be Alright.

[@ericscottstevens]

the P-47D-25RE appeared with increased range, rate of climb and acceleration and a new designed paddle-bladed propeller. At the altitudes where most of the fighting was taking place near the bomber streams, this latest Thunderbolt was decidedly faster. Above 28,000 ft, the Thunderbolt could beat the Messerschmitt in climb, unless the 109 employed nitrous oxide GM1 (Göring Mischung 1).

[@GregsAirplanesandAutomobiles]

Those are good points about the later 47s. I'll address climb performance in the next video in this series.

[@jacktattis]

@@GregsAirplanesandAutomobiles The best was P47M @ 3960 ft/min @ Sea Level and 2180 @ 32000 However the main Variant the P47D 3180 ft/min @S/L and 1100 ft/min @ 32000ft Source WW2 Aircraft Performance USAAF tests so no bias .

[@neoconshooter]

I love the "Random"? picture of the Avro Aircar in the wind tunnel near the end! Great video! A similar P-38 vid would be nice. Thank you.

[@dandel351]

Great video Greg. I could watch these for hours. I liked the B-26 at the end that seems like a very interesting plane.

[@tomw9875]

Another excellent video. Very informative and thorough.

[@BruceTGriffiths]

Hi Greg, Love the videos. At around 2:46, you mention Airspeed indicator at position 3 and I think you meant position 2. Just wanted to mention. Thanks for the great videos.

[@GregsAirplanesandAutomobiles]

Hi Bruce, you are correct Sir! Thanks for paying attention.

[@swayingGrass]

"-the only exception being the B2 bomber, which uses-" What is it Greg, tell me! "-super advanced black magic" *facepalms while laughing like a rabid dog*

[@GregsAirplanesandAutomobiles]

Of course the plane is classified, so I don't know a lot of details. However I do know that it uses multiple flush ports, that look a lot like static ports on a conventional plane. The pressure readings from those ports are fed into a computer which calculates airspeed.

[@swayingGrass]

@@GregsAirplanesandAutomobiles Haha, yeah I know that it's classified. Which is why I was laughing at myself for expecting you to know, or if you do know, that you would share that information :p

[@spindash64]

Greg's Airplanes and Automobiles Maybe it’s fed info from GPS? I mean heck, there’s so few of em that I could imagine them justifying having a satellite network dedicated per each one. This IS the Air Force we’re talking about

[@teebosaurusyou]

Pilots personal cell phone/GPS data.

[@Qrail]

Hi Greg. You explain things very well. Good job!

[@cbmech2563]

Just found your videos and subscribed . The Jug is my favorite ww2 aircraft .

[@GregsAirplanesandAutomobiles]

I appreciate you subscribing, thank you.

[@hgbarnes1584]

Really enjoy your longer videos. Thank you.

[@GregsAirplanesandAutomobiles]

I appreciate hearing that, because my next video, which is P-47 pt. 5 is so long I have real concerns about it.

[@hgbarnes1584]

@@GregsAirplanesandAutomobiles Don't be. I can assure you that 80 plus percent of your viewers will appreciate it.

[@buggerall]

Great video again, as usual, Greg! I'm more of a Spitfire person but I learn so much from your vids and love the presentation (and I'm not insensitive to the charms of the Thunderbolt). One thing that puzzles me, though: already early on during the Battle of Britain they found the fabric covered control surfaces to be problematic and retrofitted the Spits with metal. How come the Americans didn't skip the fabric from the beginning of the development/production of the Jug?

[@GregsAirplanesandAutomobiles]

Thanks. We didn't switch to metal because we Americans know better and consider our fabric superior. On a serious note, we should have taken the British example and switched earlier. There was a reluctance to get away from fabric for a combination of reasons, none of which have anything to do with performance.

[@buggerall]

@@GregsAirplanesandAutomobiles Thanks! Actually, might that be something worth a video? It probably wasn't the only plane not to skip the fabric surfaces and the reasons may be interesting... Maybe part of a video covering design choices that may not be intuitive to many. I'm thinking for example about the choice of wood for the Mosquito.

[@GregsAirplanesandAutomobiles]

It's on my list of things to talk about.

[@keithstudly6071]

F4U Corsair had fabric tail surfaces and no one complained!

[@dennismason3740]

"Fritz!" - "Ja?" - "When you chased the Jug in that dive and he left you in the proverbial dust there was a thunderclap, yet there were no clouds...you don't think..." - "Now Hans, we all know that no airplane can make that boom...that sonic boom..." - "Yes, of course, Fritz, I heard nothing...". Gravity, the worthy opponent.

[@zJoriz]

Reminds me of an old satirical comic in which a P-47 pilot says to a P-51 pilot: "Yeah you may be faster in a straight line but I bet I could out*fall* ya". The compressability issue was illustrated in another illustration by portraying a P-47 as basically a brick with a bubble canopy, falling 90 degrees straight down. With the pilot saying, "a little thing like this could ruin your whole day!" (which is a running gag throughout the series, by the way). Not sure when these illustrations were made and by who, but I think it was late (or just after) WWII.

[@jacktattis]

Quite correct the P51 COULD BEAT THE p47 IN THE DIVE

[@kenneth9874]

@@jacktattis wrong again jackyboy, the p47 was faster in level flight and in a dive

[@fishjohn014]

15:15 Isn't the speed of sound based on the density of the medium? So the thinner less dense air at altitude transmits shockwaves slower? I'm fairly positive it isn't directly affected by temperature Higher temperatures air is generally less dense (ie higher speed of sound).....but its because of the density

[@GregsAirplanesandAutomobiles]

No, Aerodynamics for Naval Aviators says very specifically that the speed of sound is solely a function of temperature. This is also the correct answer on the FAA's commercial pilot written test. Not air pressure, not air density, solely temperature.

[@nightjarflying]

Where you say Spitfire Mk IX & Mk XVI" [9 & 16] I assume you mean "Spitfire Mk IX & Mk XIV" [9 & 14] - the latter marks are what are displayed in the graphs [see time 13:34 for example] or is the graph text incorrect?

[@GregsAirplanesandAutomobiles]

Good catch. The Spitfires I am using for comparison are the MK9 and MK16s, which are pretty much the same airframes, but the 16 has the Packard engine. The MK 14 is a Griffon powered variant and not in the video, however I see that I messed up my Roman numerals on that chart, it should be XVI, not XIV.

[@heckpupper9532]

Greg you're literally like, my favourite guy ever.

[@GregsAirplanesandAutomobiles]

wow, thanks!

[@TheAneewAony]

Outstanding. Lots of supporting documentation. The focus is on diving, the one thing the P-47 could do better than German fighters. I would add that Eric Brown (RAE) at the request of General Jimmy Doolittle conducted diving tests with the P-47, P-51, P-38. Me-109 and FW-190. "The results of the tests were that the tactical Mach numbers, i.e., the manoeuvring limits, were Mach 0.68 for the Lightning, Mach 0.71 for the Thunderbolt and Mach 0.78 for the Mustang. The corresponding figure for both the Fw 190 and Bf 109 was Mach 0.75. The tests flown by Brown and his colleagues resulted in Doolittle being able to argue with his superiors for the Mustang to be chosen in preference to the P-38 and P-47 for all escort duties from then on." Of interest, as results of these tests, Eric Brown recommended that the P-38 pulled from combat.

[@GregsAirplanesandAutomobiles]

With all due respect to Eric Brown, every report I have read disagrees with the .71 mach limit he comes up with for the Thunderbolt. Republic, NACA, and other British testing came up with numbers over .80. Furthermore, there are numerous reports from both German and U.S. pilots that say that the 47 would easily out dive a 109 or 190 and those statements include situations when the planes were maneuvering while diving. Brown is alone in the belief that a 109 could out dive a P-47. Of course he also says the Swordfish was the best torpedo bomber, and that's just not reasonable. There is a reason the British didn't send and Swordfish with the Pacific Fleet to take on the Japanese. They send Avengers and Barracudas instead. I am sure he was a great pilot, and has contributed a lot, but in regards to dives speeds of the P-47, all the evidence shows that he was dead wrong.

[@TheAneewAony]

​@@GregsAirplanesandAutomobiles Yes. Totally agree. Clearly the P-47 could out dive all German piston planes. Brown's Mach numbers were not the Mach limit, but the highest speed that could be flown while still having maneuvering control. This is what Brown believed to be the reason for the USAAF's high losses (at that time). His main contribution here was giving the data that Doolittle needed for the USAAF to dump the P-47 and P-38 and reequip with P-51s.

[@GregsAirplanesandAutomobiles]

I understand that Brown's numbers were not an absolute limit. However he is the only one saying that the P-47 has maneuvering issues at mach .71. If that was true then the German planes would have been able to easily loose a 47 in a dive by simply maneuvering at speeds from .71-.75, but by all accounts I have read on both sides, that didn't happen. Most accounts say that a 109 or 190 trying to escape a 47 by diving was doomed. I don't think Eric Brown had any significant effect on the 8th's decision to go with the P-51, he isn't even mentioned in most US accounts. The reasons given for the switch to 51s are most often range, followed by dogfighting ability, and I am sure cost was a big factor as well. I have never read any statement form a US General saying that they switched to the P-51 due to superior dive performance. I am not saying that Brown didn't do some great work, nor an I saying he didn't talk with Doolittle or others, I am saying that I don't see any evidence that his input was significant in this specific area, and I am saying that his comments on P-47 dive performance are at odds with literally everyone else.

[@TheAneewAony]

@@GregsAirplanesandAutomobiles Be that as it may, one thing we know for sure, the USAAF began reequipping P-47 and P-38 fighter squadrons as fast as possible with P-51Ds.

[@GregsAirplanesandAutomobiles]

Yes, all P-38 squadrons in Europe were re-equipped with P-51s, and by the end of the war all P-47 squadrons except the 56th switched to the P-51. Of course over in Asia, it was another story with the P-47 staying on strong until the end of the war.

[@bakters]

Man, you are so biased, yet you *are* accurate. All the time you say your piece, and I'm like "fine, but you know that...", and you finally get there, but in such a way that the impression people get is not necessarily what you have said. I wish there were more people like you.

[@GregsAirplanesandAutomobiles]

Hmm, interesting observation. I'll agree that I am biased, I think everyone is a little bit, but I do love all of these planes. Some of my favorite planes are U.S., some German, and one is British.

[@bakters]

@@GregsAirplanesandAutomobiles I knew that already. ;-) Keep up good work.

[@SVTL4799]

Awesome video! Subscribed....can’t wait for the next P-47 video!

[@GregsAirplanesandAutomobiles]

Thanks Barret. I'll upload a mini video right now.

[@ranpar9786]

Thank you so much for those videos. i am so waiting for them.

[@vegardwitsoe]

"Americanian aviators: Our granite block plane is the best one to fall to the ground!" Jokes aside, very informative and well researched video :)

[@RhodokTribesman]

It's basically the definition of a weapons platform for WW2 era birds lol

[@kenneth9874]

And ironically the fastest in level flight as well

[@CncrndCtzn]

Well you are right, your comment is a joke.

[@notjackschannel5380]

From a detailed report of the P-38’s compressibility effects, the ‘uncontrollability’ at high mach numbers comes from a steepening of Cm-Alpha curve. This was caused by the P-38’s relatively thick inboard wing or 18% at the root and the resulting shocks increased (iirc) the downwash on the horizontal causing a high degree of longitudinal stability - making the elevator less effective, until it was completely ineffective - causing a crash. Later models of the P-38 included dive brakes - not necessarily to increase drag as you mentioned - but to reduce the downwash on the inboard section (changing spanwise lift) and reduce the slope of Cm-Alpha. I imagine the P-47 saw similar effects and fix the problem with similar dive brakes.

[@jacktattis]

They never fixed the Dive issues at Least NOT in 1944

[@zdog90210]

I just found your videos and I love them I can't get enough of the WW2 war birds. Also a video on the B2 and the B2 crash you mentioned would be cool. Glad I found your channel!

[@GregsAirplanesandAutomobiles]

Thanks. I'm not sure it would be a good idea for me to make a video about the B2 crash.

[@Wallyworld30]

I believe and could be wrong but the closest plane the brits had to our Thunderbolt was the Typhoon. A giant powerful fighter that was very fast. Interestingly the early models of the Typhoon had a tendency to tear itself apart in catastrophic ways. I think the fact the Thunderbolt didn't have near the growing pains that it had speaks volumes of how great the engineering was on this plane.

[@lauriepocock3066]

Just a point. The Typhoon was a much older 1938 vintage aircraft. It was flown with known issues, but in 1943-44 needs must. Brave men flew them. A better comparison would be with the Tempast which is more contemporary with p47

[@danzervos7606]

The Typhoon had a thick wing which limited top speed. The Tempest was developed from the Typhoon which had wings suitable for greater speed.

[@chopchop7938]

@@lauriepocock3066 no it isn't, the tempest was operational mid 1944.

[@jacktattis]

@@chopchop7938 And the P47 WAS NOT OUT IN 1944 Are you serious? The Tempest had been designed in 1941 but the war did not allow it to be in Service until April 44 with its Combat debut Jun 44

[@kimscheie]

Greg thanks for all your knowledge so awesome to hear

[@flcnfghtr]

In an aero eng class they told us the true max airspeed of most airframes (even where not officially known) can be estimated fairly accurately by comparing the wingplan to the mach cone. Set the cone at the tip of the nose, find the angle it makes with the wingtip, that's your design mach angle (unless something else falls off first I suppose). Makes sense from both a physics and an design optimization perspective. With excessively small wings (that fit nicely in a tight high-speed mach cone) you're giving up lift/payload, with excessively large wings you are pushing more drag and weight than you need. Just like a Panamax ship, you design for the profile you need to fit.

[@DNModels]

Lovely. You have one of the best and most informative videos on the web. Thank you thank you thank you!

[@davidkleinthefamousp]

Can plane be slowed by setting prop for smaller bites?

[@GregsAirplanesandAutomobiles]

Yes.

[@mikebeeton4982]

Yet again good genuine "griff" thanks, and as always very interesting

[@pierQRzt180]

Interesting! Thank you for your work! Question (note: all the questions and observations in comments may feed a video, as a video has more visibility than scattered comments): how common was for a pilot, especially at 10k or more feet of altitude, to decide to dive not to make any ground attack, rather to gain speed to evade an unpleasant situation? For example in case one is outnumbered or clearly unable to leave the opponent behind. In other words, beside ground attack a la Ju 87, how common was the usage of diving ? Nevermind, you answered (partially at least) from 24:15

[@thatdude3938]

Dive bombers were the only planes that did steep dives for ground attack, which is obvious once you realize that this is why they had airbrakes. Typical fighter-bomber or CAS plane had no business doing steep dives against the ground

[@robertgantry2118]

AT 13:52 - You're talking about the P-47's structural strength and integrity. THAT is one of the things I like so much about the P-47. It was one rugged airplane. In addition to that, I like the fact that it carried over 3,000 rounds of .50 cal ammo, and fired it from EIGHT machine guns. It was a big, heavy airplane, could take a beating and keep on flying, and it wasn't exactly what I would call SLOW and cumbersome either. Sure, it wasn't quite as agile as the P-51 but I think it's pros outweighed the cons by a pretty good margin.

[@jacktattis]

It was NOT agile down on the deck They lost 2600+ doing G/A duties

[@robertgantry2118]

@@jacktattis - They would have lost just as many P-51's under the same circumstances. The P-47 was highly underrated.

[@jacktattis]

@@robertgantry2118 Of course it was but it was also too large and too costly on fuel . It manoeuvred like a brick at medium to low levels And mainly its Tactical Mach was lower than the German two regardless of what you hear on here.

[@robertgantry2118]

@@jacktattis Well I think this discussion is relative to a glass of water, is it half empty or half full.

[@staszeksowikowski9039]

NACA researched that... what an unexpected turn of action

[@GregsAirplanesandAutomobiles]

I'm not following you Stachu.

[@nandovr4]

This series is great! You should put your videos into playlists. It helps when looking for all the videos in one subject. Like these on the P47.

[@GregsAirplanesandAutomobiles]

A few people have made that comment. I'll look into it eventually.

[@lauriepocock3066]

Thank you for a really excellent explanation of what is to most of us pie in the sky. Sorry, but I have to put my Brit hat on again, born in Southampton, my dynamics teacher worked on Spitfire development through the war. Your chart said Spitfire MK XI / XIV, but in the narrative you said m9 - 16. Your are right that mk 9 - 16 are equivalent aircraft, by a m9 had a 27lt Merlin engine, where as the mk 14 had the much larger griffon engine, with a similar pressurised carburettor similar to the P47. (Fuel evaporation is much better than injection according to Carnot principles? hoping you will cover that in one of your excellent videos) I need to tell you about a good friend of mine no longer with us. Born in 1923 he was a fully qualified spitfire pilot on a active squadron in 1940. On completing his tour of duty, he was a squadron Leader with a DFC, he was told the only way he could continue flying was to transfer to the far east flying p47's, which he did. He talked almost as fondly of the P47 as he did his spitfire. He was convinced that he had broken the sound barrier, commenting that you never took any notice of those brass tabs, not if you wanted to live.

[@GregsAirplanesandAutomobiles]

Hi Laurie. In the description of this video I point out that I put the wrong Roman numeral on the chart. The Spitfires I am discussing are indeed the MK9 and Mk16, meaning XVI not XIV. The 14 is not discussed at all. I'll cover the evaporation issue when I cover the Spitfire, which will happen.

[@jacktattis]

Why would he go to the far east It surely was not to fly an inferior Plane that was the P47

[@lauriepocock3066]

@@jacktattis he did 2 tours over Europe and he was told he was being promoted from SqLd to a safe desk job but he wanted to keep flying and he was told the only flying positions were in the far east. So

[@brucesmith4436]

Greg, another great and informative video. By chance, you cover the P-47s that were used in testing the Curtiss Electric transonic propellers? Or maybe the illusive P-47 with the Aeroproducts counter rotating propeller? Thanks again!

[@bradmiller9507]

I like your Style... can't wait to see your view of P-38... Compression shakes . Mach waves I have seen...traveling Over Seas...like Schielian wave old foto, just Live in Person. I called over Teammates, just for Proof. We all saw it... So Very Cool, so very Rare.

[@GnaedigerJupp]

Your channel is a gold mine! Kept it up!

[@karlp8484]

Gunther Bloemertz in his book "Heaven next stop" quotes a dive in his FW 190D (Ta 152?) so fast the ASI wound itself off the clock. That's more than 600 MpH IAS. He says elevators and ailerons were rock solid (immovable). Limited rudder control, but that didn't really help very much. He recovered by using the electric elevator trim tabs which didn't do the job (slow) until he was well below 10,000 ft. Lucky the dive started at about 40,000 ft, attacking bombers, he had continued the dive after the attack in order to escape defending fighters.

[@GregsAirplanesandAutomobiles]

The story could be true, a lot of this stuff is difficult to verify.

[@karlp8484]

@@GregsAirplanesandAutomobiles I wonder, aerodynamically, when the plane reaching higher density air wouldn't have just levelled out by itself. Bloemertz was very concerned that the very small electric motors for the trim tabs would be disabled by the effort. Does a plane that's aerodynamically stable in a very steep dive, way past DNE, level out by itself? I'd appreciate your opinion.

[@GregsAirplanesandAutomobiles]

It's possible that if it's trimmed just right it would level out on its own when reaching warmer air down low, but I wouldn't count on it. This is actually a really complex question. I may have to make a video about exactly what's happening during compressability, because I just can't explain it in the comment section.

[@karlp8484]

@@GregsAirplanesandAutomobiles That would be a very good topic. The high likelihood is that parts of the plane were transonic. Several pilots of high-performance planes in WW2 report a sudden change in control (lack of) response above a very high specific speed at a particular altitude. This sometimes coincided with violent flutter (hammering) in the tail area.

[@keithstudly6071]

FW 190D was using Junker Jumo engine, some with water/alcohol injection. Ta 152 had the Daimler Benz engine like the later Bf 190. Kurt Tank fought for years to get this engine as Messerschmidt wanted them all and had political pull. When he finally was able to get some they gave it the Ta designation for the designer, Curt Tank. The part about 40,000 ft seems unlikely as the bombers wern't that high. Some P-47 flew that high as top cover but diving from 40,000 would have them blowing past the bomber at 300+ mph closing speed and very little time to do any shooting. Read Robert Johnson's book "Thunderbolt" to get some idea what a pilot goes through getting out of a "compressability" dive. Includes feet on instrument panel pulling back on stick for all your worth and then waking up in a vertical climb as you black out in the pull up. At least in a P-47 that was how it worked for him.

[@prsearls]

Excellent discussion of airspeeds and critical Mach. I flew corporate jets for 25 years. I was surprised to learn the P-47 had as fast or faster critical Mach number than some of the jets I flew. Of course, nobody was shooting at me. I carried a pocket-size E-6b with me during most of that time. I still have that one and the big one, too. Very good, in-depth discussions in all your videos.

[@GregsAirplanesandAutomobiles]

Thanks Paul. I actually carried an E6B up until a few years ago, but the 767 has so much redundancy and every piece of metal causes headaches at the security checkpoints, so I no longer do.

[@demetridar506]

I skimmed quickly through my Alex Heshnaw book (Spitfire test pilot). He was the chief test pilot at Castle Bromwich. His 25 test pilots from 1940 to 1946 tested a total of 12,000 new Spitfires, and a few more thousands of repaired aircraft. They were flying at any weather, given the pressures of production and delivery. Part of the test flight was full throttle dives at the maximum diving speed in order to ensure the airframe, engine, and propeller controls work properly. They lost a total of 2 pilots from all causes, which were unidentified. I think this is ultimate proof that diving a Spitfire was not so dangerous. I think you should consider editing the video based on this new information. Thanks.

[@GregsAirplanesandAutomobiles]

No, that's proof that a brand new airplane fresh from the factory, or a recently overhauled plane flown by a test pilot could reach it's design limits without failing. That's very different from operational data.

[@fiftystate1388]

I'm trying to figure out what's great about the Seversky wing. It sounds like a good airfoil around a volume filled with lots of interior engineering possibility. Four 50's, dive brakes appear, disappear but another fuel tank appears, rugged, rockets, bombs, wet hard points - that kind of engineering possibility. Was there anything special about the airfoil specifically?

[@GregsAirplanesandAutomobiles]

I suppose every wing has pros and cons. There is no wing that's perfect for everything. The Seversky wing has a good balance between internal space to put things, mach limit and lift vs. drag. Greg

[@jrod1019kw]

What do you think the reason most thunderbolts flying today use the Hamilton Standard propellers and not the Curtis Electric propellers?

[@GregsAirplanesandAutomobiles]

Probably because of parts availability. It could also be because electric propellers are more likely to give you trouble. Bottom line is that I don't really know, I don't know anyone who flies or owns one.

[@jrod1019kw]

Thank you for your reply, I'm thinking you're probably right about the parts issue.

[@RadarLightwave]

Been waiting for this!

[@pascalchauvet822]

Critical Mach numbers aside, was the the roll rate and overall controllability of the US fighters P-47 and P-51(don't know about the others though) in a high-speed-dive much better due to metal covered control surfaces in contrast to the European ones which were fabric-covered and tended to inflate at high speeds, on Spitfires, Fw190, Bf109 and the like?

[@GregsAirplanesandAutomobiles]

I don't know that we have roll rates at very high mach numbers but NACA did report good controlability up to something like .78, so from there I imagine it decreases. At .83 you're not so concerned about roll rate, only pulling out of the dive gently. Of course controlling the plane at these high mach numbers probably requires a reasonably strong pilot, but the US focused on that. There was a lot of physical fitness stuff going on in pilot training. Now if you put in some weak little guy he might start complaining about problems at much lower speeds like .70 or something.

[@pascalchauvet822]

@@GregsAirplanesandAutomobiles Yes but wasn't it also reported that, say, a 109 needed excessive stick forces at high dive speeds, the Spit also dur to ballooning control surfaces but at least having a natural tendency to pull itself out a dive?

[@Mishn0]

Impressive presentation. I learn more than I need to know! Kudos.

[@petesheppard1709]

Thanks! I'm a pilot, yet I couldn't get the differences between airspeeds until watching this video.

[@GregsAirplanesandAutomobiles]

Hi Pete, I'm here to help. Glad you liked it.

[@petesheppard1709]

@@GregsAirplanesandAutomobiles Flying's easy; understanding it...not so much. :p

[@leoburke8466]

Another great video, thanks Greg.

[@bg2k625]

34:14- The Navier-Stokes equations for incompressible flow in spherical coordinates?

[@GregsAirplanesandAutomobiles]

I have absolutely no idea what that equation is. That's actually my greater point.

[@mariebcfhs9491]

basically for those who don't know, when a plane approaches it's critical mach number, shockwaves would occurs over the wing and tail, the air gets turbulent and won't stick to the wing/tail surface anymore, thus it won't get deflected by control surfaces anymore

[@clayz1]

Excellent Vid, as usual. Just one question? What are we seeing at 37:52? Thank you!

[@GregsAirplanesandAutomobiles]

That's the VZ-9AV VTOL vehicle mounted in NACA's 40x80 foot wind tunnel. It's purpose here was to serve as a test to see who actually made it to the end of the video. Good job, you did it! On a more serious note, it's one of the many fascinating projects NACA worked on. As far as we know, this one never went anywhere. Thanks for watching, and for your comment :)

[@clayz1]

An end of vid test occurred to me! So did wind tunnel, with an overhead hatch for loading test vehicles etc. I will look for more info on the VTOL. Thanks.

[@ColonelEviscerator]

How did they test max dive speeds at sea level? Did they use Death Valley?

[@GregsAirplanesandAutomobiles]

No, it's a question of density altitude. A sea level density altitude can occur thousands of feet above sea level. Just google standard atmosphere and then density altitude calculator and play with that a bit to get an understanding.