Why do the aircraft engines "stop" accelerating during takeoff?

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Have you ever heard a Boeing 737 takeoff and wondered why the aircraft engines accelerate up to a specific point, then stop accelerating before setting takeoff thrust? Why do the pilots do that?
In this episode I will try to explain the reasons behind this as well as under which circumstances you will come across this.
I hope you will like this episode and keep sending in your questions to the channel.
Check out the featured videos in todays episode, below.
BoardingNow
• Boeing 737 cockpit tak...
Turbine sound studios
• Boeing 737 takeoff com...

[@OmidRahat]

I am a frequent air passenger and used to suffer from unnecessary anxiety during flights. I spent hours and hours on flight simulators at home to overcome this problem. I eventually became and expert in aviation industry and know the source of all noises during flights and the reason behind things pilots do. Now I fly without any anxiety. I like your videos.

[@xugro]

same but i dont have flight sim so i just watched a bunch of videos on youtube about planes

[@maxislate5741]

@@xugro have any idea why the fear kicks in when the plane accelerate?

[@maximlamoureux4129]

@@maxislate5741 because you are experiencing a net force, and you realise there is no backing out now ;)

[@mikefuquay9903]

I never get tired of the acceleration on takeoff.

[@robertlafleur5179]

Mike Fuquay - I time it from the moment they release the brakes until rotation, around 30 to 35 seconds.

[@gordonlawrence4749]

I have been on a military plane doing a tactical take-off. I swear my stomach was about 10 feet behind me at one point. Then the damn thing started climbing at near 60 degrees. This was a cargo plane too (Herc with the new engines and 6 blade scimitar propeller). Basically you absolutely floor the engines on max emergency power, wait till you are at the maximum speed the wheels will take (about 80kt above normal take off I think) then go for altitude to get out of small arms range. This was at a military airshow where I managed to blag a VIP ticket,

[@mooniejohnson]

Mike, I'm with you. It's just this brilliant adrenaline rush... I'll admit that I take takeoff video for every flight I take when I'm next to the window.

[@38911bytefree]

Totally agree. I still remember the Alitalia MD-11 ... SAVAGE !!!!!!. People was complaining all around the cabin .. LOL.

[@lionnelmurimi651]

Especially on the dash 8 on short field take off 😍

[@davecrupel2817]

I love the shuddering of the aircraft when the engines are high and the brakes are locked. Those engines are screaming "GO! GO! GO!" and the plane is begging to run! And you know that when those pilots release those brakes, you're gonna go *rocketing* down the runway! Such a fun feeling for me!

[@maxmustermann194]

Basically launch control for airliners.

[@theangrynoob6388]

Well expected state of a static takeoff 🤣👌

[@mariushelland618]

Congratz on reaching 300k, well deserved!

[@leonhedman5172]

Takeoff is the best!!! I always find it so fun when I get pulled back into my seat and hear those engines roar!!!!!!

[@Milesco]

Totally agree. Especially when the acceleration continues far beyond what you normally experience in a passenger car. In a car, even (or especially) when you accelerate briskly, it lasts for only a few seconds. But with an airplane, you keep accelerating and accelerating, going faster and faster and faster, for 30 seconds or more. It's really cool. 😀

[@zkwip8100]

Thanks for explaining the ice shedding too! I was listening to ATC at schiphol last week and was wondering why the planes got permission to spool up so long before before being cleared for take off, now it makes sense.

[@CP2468]

This channel has been amazing for me. Starting to see that during flights I am wondering less and less about what's happening because I have a lot of answers about little nuanced things that would have previously made me nervous. Huge thank you for that :)

[@darioinfini]

You guys are amazing with all the nuanced details you have to know to fly these things well and safely.

[@Gilles45]

On my last flight on a 737, the pilot did the thirty second thrust you mention, but he was nice enough to inform the passengers that this was normal and recommended by Boeing for the conditions prevailing that day... now I know why! 👍

[@kennethpitman1397]

Thank you for that explanation. I have wondered about that many times.

[@brassmanone]

Short videos are fine. You always present information very well no matter how long the video is.

[@ritvikvaishnav3472]

nice one petter. congrats for 300K!!!

[@adamseab]

Completely didn’t think about this as a reason. I always thought it was to test the engines briefly, before going full ToGa to ensure that temps/pressures were normal. Great video as always 👍🏻

[@trevorjameson3213]

Excellent, very interesting to learn this! I always wondered about it

[@hectorrivera1719]

Thank you for all your great info all the time!! Keep up the great ENERGY!!

[@azmike1956]

Great explanation on differences in engine spoolup. Even after decades of engine maintenance & testing there is always more to learn!

[@wilhelmtaylor9863]

Back in my Vietnam days we flew on commercial airlines with military pilots. There is quite a difference in how they flew a plane full of troops compared to civilians. The takeoffs were usually at near full power and the landings were MUCH steeper. The plane would turn after takeoff while still very close to the ground, which is truly scary. First time into Tan Son Nhut in '68 in a 707 the runway was being mortared. We came in from 41,000 feet to ground in what seemed like a simple drop and a lot of guys were white as sheets grabbing on to the arm rests. I recall the pilot's words over the intercom, "Ah, gentlemen, we'll be coming in fast due to some ground activity. Be prepared to leave the plane as soon as we pull up to the hanger. Grab any dufflebag on your way under the plane - you can sort them out later." I've never experienced a plane stop so fast. He was off the ground a few minutes after we were out.

[@David-hw5xk]

I had close to the same experience leaving PSAB back in 96-97 time frame. We were in an ATA L-1011 Tri-Star, and on take-off the pilot raised the AOA quite steeply for a civilian airliner and circled the air base perhaps 5 or 6 times at what I presume was full thrust, until the plane reached a sufficient altitude so that Stinger missiles had no chance of intercepting the plane on fly out. It was quite unnerving given the fact that they did not notify us prior to takeoff that they were going to do that, added to the story from the Air Force folks 6 months earlier when we initially flew into theater, that an AH-64 had flown out and killed a insurgent armed with a manpads rocket that was targeting flights coming into the base. At the time I Initially thought that was simply a story to razz the incoming soldiers, until months later when the giant voice system on the base announced that they were about to detonate an IED, only to be followed by a rather large boom seconds later. Not only did this happen once, but several times during our 6 month tdy stint in that oven of a country. "Yeah but it's a dry heat" says Corporal Hudson. NOT. At 120 degrees, it doesn't matter. And those lovely showers where the only temperature is scalding hot from those massive water bladders baking in the sun. Those were the days.........

[@rocnnrollbus]

@@David-hw5xk we would do tactical approaches in the C-130s into and out of PSAB back in the day. Fun times. Flying Crew Chief, C-130. 363rd EAS, 2000.

[@David-hw5xk]

@@rocnnrollbus Nice, flight crew would have been a fun job. I was TDY to a SATCOM facility for 6 months. Managed to get there RIGHT in the middle of summer. Thought I wandered into the jet blast of one of RB211's when we arrived, then I realized that was just Saudi. But hey, even though we never left the base, I did get quite the exhilarating ride aboard a Blackhawk with a pilot that I swear thought he was flying in an AH64. Didn't think a Blackhawk could maneuver like that.

[@scott729]

Nowadays people hear you guys coming from thousands of feet away due to all the noise your dragging steel balls make .... good god, can't even imagine being involved in any of this stuff and I am no pussy. Well, compared to ya'll maybe I am a little bit. Would do it if I had to I suppose. Hats off to ya

[@AFmedic]

@Wilhelm Taylor - When you mentioned the steep turn after take off, my first thought was "taking off from NKP, Thailand in C130 Hercules. Thank God those days are long past.

[@StevenNassibian]

Thank you, I always wondered about this.

[@jjsifo1]

Good thing you are doing here with these videos, students and people interested in aviation learn something new,and you keep sharp and profficient in the theory and ground school aspect, don't let anybody discourage you . JJ , retired Law Enforcement Pilot , Fixed & Rotor Wing.

[@buddyclem7328]

Congratulations on 300k subscribers! Great video captain!

[@prjndigo]

To point out: I don't think he mentioned that because the engines are air compressive devices the local wind conditions, heat over the runway and even the aircraft's angle to the wind on the runway can make the spool-up not only vary but also make the total thrust output vary. So they spool the engines until the engines are creating their own small "climate" of wind and density then adjust them for those conditions. It can be especially strong on smaller twin tail engined aircraft.

[@elsamarjanen7841]

Excellent video!!! ✈️🛫

[@gracelandone]

Thanks. Always doing your part to alleviate nervousness of reluctant fliers so that we may eventually find the joy of flight as you have.

[@Blissenobiarela]

Always fantastic!!! Thank You... All the best from Brazil!!!

[@rishabhmehta2477]

I always wondered about why pilots say "stabilized". Now I finally know. Amazing video mentor.

[@TonyP9279]

"Stabilized" is also a term used on final approach when you are 1,000' AGL, which means you have flaps down, gear down, and on a steady descent rate.

[@rishabhmehta2477]

@@TonyP9279 Amazing fact. I was unaware of it until now.

[@OK-iq7ls]

Thank you so much for answering this, I’ve been wanting to know this since a very long time, amazing video as usual.

[@RahmanSajid]

Awesome video Petter, really enjoyed this one, very informative for us trainee pilots :)

[@tylerg7567]

I truly love your videos! Thank You!

[@Geigerzaehler]

I once experienced that ice shattering technique you explained. I thought it was kind of a "heating up" or something but never really knew the reason actually. Nevertheless I wasn't scared but excited about feeling the power of that jet engines.

[@earlystrings1]

Interesting as always. I thought you were going to discuss thrust reduction climbing out of airports with extreme noise abatement rules. I experienced this once out of SNA and really thought we were going around.

[@rstknives2423]

Great video, great info. Thanks!

[@aqimjulayhi8798]

This explains why sometimes I hear that 'double spooling' sound of a plane taking off. Great video, sir!

[@JoseOrtega-XOR75]

You missed the part that also, we avoid engine stall, as some engines (ie JT8) have a tendency for stall if you accelerate to fast.

[@em1osmurf]

stabilizing! synchronous speeds on turboprops is pretty crucial too. they each have an indicator which will show which one(s) need tweeking. technology probably has taken the human equation out of this, as this was decades ago. i found out about it riding navy transports--you don't get those puppies synchronized, and you'll very soon find out where all your tooth fillings are! another good vid.

[@littlewhiteangora1374]

Excellent explanation! TY.

[@airfoxtrot2006]

Very nice video Mentour!

[@bigtop1967]

I love it when they keep the brakes on with engines running....love how you get pushed into your seat when they let go! Are you sure that only happens when de-icing? I'm sure I've experienced this when not cold... Love it!

[@amirjkhan8639]

yes, you are right, they use this method also when the runway is short .

[@ryanportzline9239]

Wonderful video. Is it possible for you to please do a video on “Rudder Dancing”? I’m noticing quite a few pilots, on what seems to be struggling with keeping the aircraft on the centerline during takeoff roll. Even on calm wind days. Thanks

[@eromadroleromadrol5171]

Excellent, as always !

[@richardsisk1770]

Thank you for all the interesting knowledge that you share here!

[@B1970T]

Hi Mentour: I would like a vid on transport plane wipers , rain repellents and speed limitations for use. Correspondingly, the components of windshield construction. Thanks. Nice vids.

[@aviationforlive7434]

You are going to have 300.000 subscribers in a view hours, and great Video! I wondered why pilots do this for a while

[@MentourPilot]

Excellent! Thank you!

[@Hubjeep]

I just subbed!

[@morninguvnuh4769]

just subbed to help

[@THYB737]

*you are going to have

[@aviationforlive7434]

Hayrullah Ceylan ok thank you :D

[@Nilguiri]

Interesting, informative and entertaining as always, Petter.

[@kirti7659]

Loving the content man!

[@ambarishtirumalai5298]

Yes, I had observed this... The reason is really fascinating 😅

[@umeshp.2454]

How come you were not aware of such simple things. These are common things during takeoff and stabling the plane.

[@gordonlawrence4749]

I could be wrong but I was under the impression that as well as the potential asymmetric thrust issue (which was far worse on turbojets I have been led to believe), there is also a wear and tear issue. IE some engines directly use engine power driving the lubricant pump (jet lube oil looks a bit like water it's so thin). IE you let the engines stabilise at about 40% thrust (which can be 80% RPM on some engines) to get the oil pressure in the thrust bearings flowing hard before they take full load. The thrust bearings are not much bigger than the palm of your hand and take up to 50,000 pounds push as well as whatever rotational force is caused. Without high pressure oil they would wear in no time from increased friction and the issues associated with friction heating. I believe most since the late 80's use electric oil pumps very similar to hydraulic pumps for oil pressure, but there are a surprising amount of J79's still in use as well as other even older designs (RR Olympus for example). Newer Olympus have electric pumps but they are originally from the 1940's, way before electric pumps were used. Some of those old engines are still in use (on ground installations for power generation mainly).

[@robertheinkel6225]

Gordon Lawrence Turbo fans have more power than turbojets, and losing an engine has a bigger effect. On the KC-135, we switched from turbojets to turbofans. The swap required an automated rudder system to control the rudder in case of engine failure, because a pilot could not react fast enough during engine failure to control the plane without the automated rudder.

[@gordonlawrence4749]

How is that even relevant? When you are talking about asymmetric thrust, the engine management systems for the old turbojets were nothing like as good as modern ones used on turbofans. Therefore in a situation where you are spooling up you are more likely to get a bigger differential on turbojets compared to turbofans.

[@emaildenis]

Excellent subject! Thanks Capt.

[@sonnyzeitgeist2570]

Great explanation. Thanks.

[@RedArrow73]

5:40 - Could also be framed as Engine FOD Prevention.

[@roberthagedorn290]

Thank you for the video--very informative. Now I know. Back in the 50's & 60's when the 707 was introduced and runways were short, flying commercial was very exciting. Takeoffs were at full power with us passengers literally plastered against our seats and our faces being pulled backwards, as if we were in a spacecraft. Upon landing, the engines were immediately fully reversed, so if someone did not have their seat belt fastened, they would probably end up on the floor after sliding out of their seat. Much different today. I miss the old days, but this manner of taking off and landing must have been tremendously hard on the aircraft, especially the engines, but also the entire plane. Nowadays, with long runways, it sometimes feels for a while like the pilot is going to drive to the destination instead of fly, and engines are only briefly reversed upon landing.

[@davidrobins4025]

Thanks for the clear explanation.

[@crimefacelaw8167]

Great piece of info!

[@JetNmyFuture]

712 likes with ZERO dislikes is an amazing accomplishment! Love this series.

[@gordonlawrence4749]

SSSHHHH!!! The trolls might notice!

[@alc7692]

Also, the 30 second "shuddering" period will also build the temperature of the Bleed Air in the Inlet Guide Vanes, aiding deicing.

[@Zero-sj8qh]

What a fantastic job! How lucky you are! Cheers !

[@stevenshackelford1937]

You do a great job of explaining - TY !

[@wildzach]

As a kid, i was always intrigued by the 737 NG, how it would spool up really hard, then pause and sound like it's spooling back down, then spool up again even harder. CUUUUUUGGGGGHHHHHHHHpssssssuuuuuuuurrrrhhhhhh...............PSSSSHHHHHHHHHHHHHHHHHHH On one of my recent flights, i think they spooled it up to 40% and then held it there for a considerably long time (in hot weather) before going full. Not sure if they were unsatisfied with the different spool up rates or something unrelated (maybe Tower had more things to say)

[@eaglegrip6879]

Right. In hot weather, the ambient air is less dense, causing the jet engines to perform a little slower than in cold weather. In fact, some US military aircraft used to have spray nozzles mounted near their jet engine intakes (like the KC-135 A/C... with its J-57 engines, for example). During hot weather, those spray nozzles would spray a fine alcohol/water mixture mist directly into all the engine intakes to make the inlet air pressure colder and more dense during takeoff. That mist increased engine performance by as much as 25%. Just FYI. Hope this helps. Cheers!

[@zoperxplex]

For someone not about to enter pilot school that is a question that has never crossed my mind.

[@gordonlawrence4749]

Personally I'm a curious bugger and want to know everything. One of the most annoying things to me is that I don't, so this question has crossed my mind many times before I started work in aerospace.

[@TomF1970]

Great explanation. Always wondered about that.

[@xorinzor]

The next time I'll be flying will be such a different experience, just having learned so much from your videos and knowing what's going on. Absolutely love it! Keep them coming :D

[@mizzyroro]

I thought the reason for this was after Air Florida 90 where the engines were affected by ice and never reached takeoff thrust. The FO noticed the engines had not reached the takeoff power settings and called it to the captain's attention but the captain did not listen. From since then, the requirement was that you advance the throttles to about 40% to ensure the response is as it should be then advance to takeoff power. That's what I know.

[@gatesmw50]

Fakalasi Palm 90 's cockpit crew never turned on the engine anti ice system prior to takeoff. That was also a contributing factor, and an inexcusable error.

[@michael2k3d48]

I notice it. Congrats on 300k subscribers.

[@leefithian3704]

Very informative, learned something new !

[@69stall]

thanks Petter, you're the best on you tube channel!

[@deeanna8448]

I'm flying today. I'm going to see if I notice this!

[@Khemani_RL]

Dee Anna how does your comment say 22 hours ago when this video was I just uploaded

[@washx2k755]

LittleSophia _ because he is an patron supporter

[@Genthar]

Patreon supporters get early access.

[@deeanna8448]

Time travel😂

[@jonasmller6962]

Dee Anna Have a nice flight!

[@oni101]

Is the thrust percentage directly linear to the RPM percentage, or is a curve or even an exponential curve? Thanks for your great videos.

[@Lozzie74]

Yeti it is a cubic relationship (thrust is proportional to rpm^3)

[@FlyingInlines]

Great video! I noticed that on my flights this Monday.

[@johnkelley9877]

Great information! Thanks for sharing this.

[@19carrot84]

Thank you for taking the time to make a video during your annual leave.

[@RV6Pilot]

I do the same thing on my piston airplane, but for a different reason: if I go to full throttle before the plane is moving forward, the prop blades pick up any gravel and/or sand from the runway and it nicks the leading edge of the blades. I always assumed jets were doing it for the same reason.

[@buddyclem7328]

Thanks for the info! I imagine that would be even more important on a gravel runway.

[@younessbouzelfane1479]

Great video as always. Hope to see you in Tangier .I know you fly their very often

[@737driver]

I love the sound of the CFM56-7B when you advance the throttles. First the heavy buzzing sound when it revs up through 30% and after some seconds you hear the soft whine (love it!) when it reaches 40-45%. And when it's stabilized, the pilots unleash the power! The howl as it revs through 60% turns into a brutal roar when it's reached take-off thrust! Eargasmic!

[@b1squitz551]

Here's my question: under the front gear on some planes there is a red sign saying "no tug". I have especially noted that on the A350. What does it mean. My theory is that on those planes you cannot pushback using the bar they attach to the gear. Am I right?

[@hamburgerquieddje3898]

B1squitz not quite, it indicates the tug truck to not go further and cross that line with the towing bar, since it is the maximum of the steering angle when towing the aircraft.

[@djvanzz]

I was always told it was to prevent engine flameout. If you accelerate the engines to fast you can flood them and cause a flameout. I'm assuming thats not a problem now because the computer manages a smooth linear spool up?

[@MrGeekGamer]

Always fascinating to hear these details.

[@paohlostorm6194]

Magnific video, Captain!!! A brazilian fan.

[@Zany4God]

Excellent as always. Me and my little C150 never noticed this phenomenon. :-) What about military aircraft? Single engine and multi? It seems they also do a run-up and after a certain point the AB is lit and the plane rolls down the runway.

[@mytech6779]

All turbines are slow to spool up, you don't want to waste runway rolling along at half thrust.

[@jort93z]

Its really only important if you have more than one engine i'd think. Because you cant have asymetric thrust with one engine obviously.

[@souocara38able]

The further apart the engines are the bigger the potential issue. When they're very close together the issue is almost non-existent. Think of most fighter aircraft F-14 F-15 F-18 F-22 the engines are are very close together near the center of the plane. I haven't researched this recently but I do remember cases of early f-14s crashing because as they were approaching the deck to land they would apply power and if 1 engine didn't respond properly it would cause the aircraft to roll and lose control

[@Zany4God]

I have a vague recollection of some fighters throttling up to X% and then full military power, and then AB. Is that correct? I have vivid memories of the F-111's firing up the AB's with the brakes on and the pilot's teeth clenched(not true) and the length of the flame was adjusted out of both tail pipes and then she'd roll down the runway. What a thrill.

[@6105boe]

Isn't it also just a case of throttling up to a certain % to make sure everything is looking normal? While you're still standing still there's much less to worry about than when you're already rolling so to my mind just that alone would justify the little bit of extra spent fuel.

[@CyclicPilot]

I never knew the reason for this, but that makes sense! I'd guess (as an engineering undergraduate) that the acceleration rate of the engine has more to do with the N2 rotation speed than the fan speed - turbine engines work much more efficiently at high pressure ratios, which requires high compressor speed, and any extra friction in a worn out engine would have most effect at lower power settings. I was once on an easyjet flight where they didn't seem to pause at 40% on takeoff - there was an aircraft on final so they may have been told to "expedite"! It seemed they taxied onto the runway with ~40% already set, then went straight to takeoff thrust without stopping.

[@christopherwilson6527]

Iwan Wrigley most thrust comes from the fan. The efficiency is mostly lost by increased gap between the blades and the case. Bigger the gap the more air bleeds past the blades and not working on turning the blades, so less efficient. Old engines actually have very little turning friction. Our engines can keep turning for over 5 minutes after cutting off the fuel at idle.

[@CyclicPilot]

Thanks, good to know!

[@JeremyCoppin]

Incredibly interesting. Thanks.

[@alexsantiago357]

Early congrats on 300k subs Mentour

[@KJ-ml2zb]

Hello, Air Traffic Controller from Hong Kong here. I got question I would like to ask. Does a slow taxi speed reduce the fuel consumption? The situation was, the weather was suddenly very bad with thunderstorm and aircraft at the holding point did not want to depart at all. But some aircraft had already commenced pushback and would expect an airborne time of 30 minutes later.The time needed for these aircraft to taxi from the terminal to the runway holding point would normally take about 5 to 10 minutes only and then they would be waiting at the holding point( or moving forward in the queue along the taxiway). In such case, does a slow taxi speed reduce the fuel consumption if the airborne time remains the same no matter how fast they taxi? And, is there any ways to reduce the aircraft fuel consumption between pushback and take off? Thank you! I like your videos! Your videos help me to understand what pilots think and want so I can provide a better service

[@KJ-ml2zb]

well i know this well but this doesnt answer my question but anyway thank you

[@stevokennedy2383]

I don't think petter ( mentour pilot )replies to any questions on here!

[@hangoszto]

@@stevokennedy2383 he does occasionally here and on Instagram

[@jimmartin3697]

After pushing up the throttles to start the aircraft moving, the throttles could usually be brought back to idle and the aircraft would continue to move at a slow but decent speed. If you wanted to taxi faster, you would have to push the throttles up farther or longer, using more fuel in the process. A continuous, mostly at idle, taxi to takeoff is ideal. Stop and go taxiing uses a lot of fuel. Any large aircraft, especially Boeing 767s and larger, burn a lot of fuel to start moving, so once moving you want to keep moving. The advantage of sitting at the gate is that fuel consumption can be zero if using ground based electrical power and air conditioning. Sometimes the gate was needed for another aircraft so we would have to push off the gate, start engines and taxi to a holding point or get in line for takeoff. We usually had enough contingency fuel for short delays. If we thought the delays would be extensive we would only start and taxi with one engine, reducing fuel consumption about 50% (on a twin engine aircraft, 66% on a trijet). Weight was a consideration. If we were very heavy, we had to start two or more engines to preclude jet blasting everyone and everything behind us. If during taxi and stopped at a point where we could expect to sit for a long time, we could shut down some or all of the engines and use the the auxiliary power unit (APU) for electrical power and air conditioning. The APU used very little fuel compared to the aircraft engines. We always had to monitor fuel consumption and consider how long it would take to start the aircraft engines and warm them properly before takeoff. Cold weather operations with ice and snow added the complications of getting deiced with the proper mix of fluids, computing the maximum time before having to takeoff or getting deiced again. In rare instances we would have to return to the gate to get more fuel AND deiced again. If we were the only aircraft at the airport it would be easy but at bigger airports like Chicago, New York, or Tokyo you became one of many needing a gate, fuel and deicing. Other time calculations were crew duty times and ground delay times. Crew duty times to see if the pilots and flight attendants had enough time to endure the ground delay and fly the flight to destination. In the U.S. there were rules that could force the aircraft back to the gate after a certain amount of time away from the gate without taking off (Not a factor if the aircraft never left the gate.).

[@tigerrx7]

Great explanation. We (Performance Engineers) endorse this 50% N1 prior to setting T/O thrust as this helps with the thermal stability of the engine and subsequently sufficient Time On Wing margins

[@fish4kbcf]

tigerrx Time On Wing?

[@danielwhite96]

BassinWithBuck time between rebuilds

[@rickvia8435]

Good work on all your vid explainations

[@akarrer66]

Interesting, thx for the explanation

[@gleaveinjapan]

Thanks for the information. I remember back in 1974 the take offs were very different, The planes would seem to rev up to full throttle but the brakes were on, then the brakes were released. This was in August ( Nothern summer). Planes were DC10, Boeng 707 and Lockheed L1011 why has the take off proceedure changed to a rolling take off?

[@GlassTopRX7]

I believe that has to do with the type of jet engine. Those early jets used turbojet engines, and standard turbofans today airlines use high bi-pass turbofans. As result of the larger mass of the inlet fan it takes them longer to spool.

[@josephgaviota]

@@GlassTopRX7 And, the by-pass makes them quieter, is that true?

[@GlassTopRX7]

Yeah. @@josephgaviota

[@peted3637]

We got this one day leaving Canberra for Sydney in some turbo-prop plane, probs a Dash-8. There was only about 6 passengers on board, the pilot held the brakes and brought the engines up to high speed for about 20 seconds and then released the brakes. It was the hardest take off I'd ever experienced! The thrust was truly epic! :)

[@Zickcermacity]

I definitely notice this pre-spool in a 777 or A-350 sized machine with engine nacelles big enough to fit a campaign promise through. ;D It's good to warm the choir up first before blowing out the church windows!

[@louisluqueromero2914]

As always a great video!!! Thanks👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍

[@danielg9805]

Great videos everything is explained so clearly :)

[@benjaminduperreault4447]

Mentour I was wondering something about asymmetric thrust. In case of single engine failure do you cut the other engine to avoid falling into a flat spin? If so do you try to "glide" the rest of the plane somewhere into the water. If you don't cut the engine, what KEEPS you from falling into a spin?

[@StepSherpa]

Vertical stabilizer and rudder prevents this to some extent

[@robertlee9395]

The aircraft is designed to fly on either engine.

[@DJChizzlesworth]

In the event of single-engine failure, the pilot will have to command opposite control input in order to keep the aircraft flight stable. Aircraft are rated for their ability to fly on single engines, which Mentour covers in the video about why we don't see more tri- and quad-jets (I think!) - they have an ETOPS rating, which is the maximum time that the aircraft can be from a suitable airfield in the event of an engine failure. As engines these days are highly efficient and stable, the highest ETOPS rating now is ETOPS-370 for the A350, so it can be more than six hours away from a suitable airfield on single-engine running. That isn't to say that aircraft will fly for that long on a single engine, just that they can.

[@souocara38able]

I'm not a pilot but I'll add what seems logical to me and maybe someone will correct me... we'll see. So it seems interesting that they run up the engines to 40% to avoid asymmetrical power however if an engine completely fails they can continue to take off. I understand your confusion LOL. The key I believe is when this engine failure would happen. If it happened before V1 they would not continue the take off. This part of the takeoff sequences also when they would be concerned with the engines producing asymmetrical power which is why it's important for them to try and avoid it. By the time they get to V1, the engines have been at take off power for some time and will be equalized if everything's working properly and again if everything's not proper they would abort the take off before V1 Ah, another thing to consider is that by the time they reach V1 they are going quite fast so the aerodynamics of the plane are what will keep it under control when an engine fails. As described earlier they don't have this benefit at lower speeds so asymmetrical thrust is a much greater problem

[@Avgeek1564]

Hi Can you please explain what the TOGA button actually does? I thought you just pushed the throttles to achieve thrust required? Thank you.

[@avamendez1272]

stands for takeoff/go around. the actual toga position sets the full rated thrust of the engines. unless the runway is contaminated, a flex takeoff setting (a value more than sufficient for takeoff but below maximum is set) the figure is derrived from software on the EFB. it is proprietary to each carrier

[@maninthecab]

Ava Mendez Not quite , the TOGA switches will advance the thrust to whatever level has been entered into the system, full or de-rated ; Flex is an Airbus term which also sets whatever thrust level has been pre-entered.

[@klobiforpresident2254]

@@Sterlingjob Airbus just chose a different name, anywhere else that's what toga is.

[@klobiforpresident2254]

Deleted due to retardation.

[@itzthedude971]

Klobi for President It's the same on every other modern aircraft. The fmc will determine how much thrust is needed for the take off run when the variables are dialed in. Variables such as Air temp , wind speed weight and many more. I don't need to explain further but the point is, Airbus or Boeing it's the same take off techniques.

[@wolverineracing8896]

Great videos, thanks !

[@Algonquin7791]

My biggest question was answered in this video regarding takeoffs! Thanks a lot✌️

[@living4christ]

I like getting pushed back in my seat and hear the engines on toga during takeoff. Take off is my favorite, I like to get flights with as many connections as i can when I fly to experience multiple takeoffs. Is there any way you can make a takeoff push you back in the seat more than it usually does?

[@MentourPilot]

Yes, normally we de-rate the engines and use as little thrust as possible to save engine life. If we used full thrust you would notice 😉

[@BrilliantDesignOnline]

I love when you push my eyeballs back in my head. And when pilots do a bit extra ascent angle on the climb-out; I know most passengers don't appreciate it (But I do, a 737-max TO would be fine with me, and highly grin inducing).

[@mytech6779]

Yes, buy tickets on the B757-200 from airports with shorter runways and surrounding mountains. For commercial airlines this will be the best acceleration and climb performance.

[@SaltwaterC]

The only way to get decent amount of thrust is on airports with relatively short runways. Taking off on an A320 on a 6692ft runway is always fun. The pilots spool up the engines with the breaks on, then hit the bricks like they sat on a wasp. Now bear in mind that an A320 at MTOW requires bit more than 6800ft to take off. They don't take as much fuel though since the longest flight off that airport is little over 3 hours.

[@segwaydave]

‘Push you back in the seat more than it normally does?’ Gain 35 Lbs? ;)

[@WarpRulez]

I notice that there seem to be two independent levers. Is it possible to operate them independently? Is there any situation where you deliberately want more thrust on one engine than the other?

[@buddyclem7328]

You use asymmetrical thrust to overcome rudder hard over, or to steer the plane after loss of all hydraulics.

[@FerralVideo]

You also would want to roll back, and then shut down, an engine that has failed or is having a mechanical problem, but the other one is still running okay.

[@f-j-Services]

Yes a plane had lost hydraluics and they used engine thrust to change direction and pitch.

[@gatesmw50]

@@f-j-Services Exactly! United Airlines DC10 crash Flight 232 in 1989 ! That is how they lined up with the runway when they lost hydraulics.

[@f-j-Services]

@@gatesmw50 Yep! :D

[@bobg1069]

Excellent video, Just today, I was explaining this very thing to my aviation students, your video was excellent in reinforcing the teaching point,. many thanks,

[@divyachandhok3895]

Thanks! Enjoyable, as always.

[@VladoSK]

In many videos from a cockpit I have seen the climbing phase done at V2 speed which is only a bit faster than the stall speed. Why is it that? Is the reason to get to the cruise level as fast as possible with least fuel consumption? I suppose climbing at 250 KIAS would take some time (owing to the small pitch angle) and a cause a higher consumption due to higher drag and denser air. Right? Btw. I watch your videos, they are very educational, professional and yet very comprehensive. And I am toying to enrol to a PPL(A) course. Thank you.

[@realulli]

Usually, the climb is done at the "best glide speed". That is, at the speed the plane generates the most lift with the least amount of energy expended. Basically, flying is all about energy. The engines turn the chemical energy stored in the fuel into kinetic energy (speed) at a certain rate. The angle of climb turns the kinetic energy into altitude. At higher speeds, you don't need as much angle to get the same climb rate. So, the plane will climb at roughly the same rate independent of the airspeed (somewhat slower climb due to the increased drag, but not that much), but yes, mostly they climb as fast as possible to get to an altitude where the engines run more efficiently.

[@VladoSK]

Thank you for explanation. I have experimented many times in my X-plane 11 simulator with B737 and indeed when i set the cruising altitude, use LVL CHG button and set the speed to V2 speed the aircraft is climbing quite rapidly. I might not be fastest but certainly the engines are not set to full thrust. I have tried to play with the Vertical speed hold but I consume a much more fuel. Needless to say that some pilots told me this is not exactly a safe way how to climb.

[@realulli]

Ok, I guess a bit more explanation is in order. There are several speed values that are useful. There are V1, Vr and V2. You need those only during takeoff. Vy is the "best angle of climb" speed, which means, you have the maximum altitude gain with the least horizontal travel. That's probably pretty close to V2. You use that speed during a short field takeoff to get over an obstacle. Then you have Vx, which is the "best rate of climb" speed. I suspect that's also the best glide speed, but I'm not a pilot, either. If someone out there knows, please tell :-)). This is the speed you should set when climbing via LVL CHG to gain maximum altitude in minimum time. The reason why vertical speed hold is dangerous is that the auto pilot will try to hold that climb rate by adjusting the pitch. If you set the climb rate just a hair too high, the autopilot will happily pull up until the plane stalls.

[@rydermarkey8274]

@@realulli great info but Vx is best angle while Vy is best rate.

[@realulli]

Thanks for the correction. I keep mixing them up...

[@h0107]

Iv’e never been on a winter flight. Do they announce that they’re doing the ice shedding technique over the PA, because I imagine many passengers would be worried.

[@robertlafleur5179]

H010 - On a winter flight from Montreal they announced it. The plane was shuddering, it seemed the tail was moving from side to side.

[@algrayson8965]

@Gun Nut- When the plane takes off out over the ocean then banks so far over that you can sight right down the wing to the city below it's a little scary the first time.

[@spankyfingaz]

Greetings from Kenya Mentour! I'm a lawyer who's always been fascinated with the goings on in the cockpit during my travels and I must say your channel is amazing. Keep it up man as we race to 300k!!!!

[@andraslibal]

Interesting detail that I never thought about before. Ties in well to the previous videos you mentioned.