How To Forward Slip an Airplane

[@daffidavit]

Keep in mind that during slips, the pitot tube is also slipping with the plane. The fuselage blocks the pitot tube from a direct airflow giving an inaccurate airspeed indication. I've seen the error as much as over 20kts in some situations. So don't rely on your airspeed indicator for accuracy during heavy slips. DPA, CFIA

[@GarryWing]

Good point. In most light trainers there is also only one static port, which may or may not be in the airstream. In my Cub, the static port is behind the ASI inside the cockpit, so airspeed will read between 30 - 70 MPH while slipping --- next to useless.

[@daffidavit]

Nice to meet you Garry. Good video. Good lesson.

[@Alex-us2vw]

I was about to post this. The PITOT tube is way off while uncoordinated and 20knots slower indicated is pretty much a given during a full deflection forward slip. Right when you release the inputs can see the indicated airspeed just shoot up.

[@musoseven8218]

@@GarryWing Thanks for a great video and the extra info (above). A quick question about not applying throttle (height) which is understandable on finals/approach, am I correct in thinking when I see Eg, an Extra 300 flying in the slip angle (uncoordinated) at the same level along the runway in a display that the pilot has to apply throttle (constant) so as to maintain such a manoeuvre?

[@benderaviation]

@@Alex-us2vw Thanks! That explains why I so fast short final after learning slips. Should we just have it trimmed for appropriate speed before (80 kt is what my instructor suggested in the 172M) and let the plane fly itself at that speed in the slip?

[@richardgregory9777]

Gary - Thank you for the great videos! I am a private pilot with a few hundred hours, and really appreciate the 5 minute clips / lessons! Great refreshers! Thank you!

[@VibeWeaver88]

I've been watching your go around video all day today. I'm teaching go arounds at a CFI job interview tomorrow, and got excited when I saw you just uploaded another video. I love these videos, they are very succinct and to the point. Keep uploading them please!

[@bruce2357]

My powered airplane instructor didn't teach me much about slipping if any. My glider instructor, which came before my power training taught me loads about slipping. Turning while slipping was even taught. While downwind at the end of my SEL check ride we were cleared to land. The examiner declared I had lost the engine and my flaps were inoperative. We were in a Piper Cherokee which has mechanical flaps and it's extremely rare to have a flap failure in a manual flap airplane and I relayed that to the examiner. He said he didn't care, land the airplane without flaps. I don't know how uncomfortable he was with my aggressive slipping, but we made the runway and I passed.

[@johnscott1621]

My 15 year old grandson just took his first lesson in a 182 Cessna. He's sitting hanging on your words. You make GREAT instructional films. His head is going up and down. Thanks from both of us

[@1stinsonguy]

Well produced, well demonstrated, and well narrated video. Thanks, Garry!

[@Mrfrenchdeux]

Great explanation. Simple and to the point.

[@allanmichael5548]

Nice work Gary! Your explanation and in-flight demonstration made a sometimes confusing subject crystal clear.

[@CabviewHolland]

This makes everything clear. Thanks for the demonstration!

[@nintendokings]

Awesome video Garry!

[@jimrees1778]

After some practice with slips, they become second nature. I practiced most maneuvers in a Cessna 152. Slips can save you a lot of time and fuel over the years by not having to go around, etc., should you reach your destination with more altitude than planned, plus they are just fun to do and practice.

[@DavidSmith-mk7qo]

I just came across your videos on the the tube. Nice job explaining and demonstrating the manuver.

[@voicetube]

Having seen a video on the 1983 "Gimli Glider" incident (where a dude had to land a 767 that had run out of fuel In a retired Air Force base in Gimli, Manitoba) brought me here. The pilot had to use Forward Slip as they were a bit excessively high above the runway on approach (and their only chance to land safely was that particular and single approach)

[@damondeluca]

Awesome Gary. Thanks!

[@peregrinussolutionsllc6010]

Great video Gary! Thank you for sharing your knowledge and experience!

[@RobertBremmer]

Nicely done! Good narration and planning and I personally love the San Diego background, I used to fly and teach out of Gillespie field.

[@tobewealth]

Thanks for great help.. plz keep uploading videos capt Garry.

[@adamaltawila2]

Sir,, you are professional pilot 👍 Short videos and you will have clear idea about the lesson. Please keep posting lessons, they are very helpful.

[@jeanbascout]

Can you add flaps and or lower landing gear while in a forward slip?

[@GarryWing]

Yes; unless it's prohibited in the POH, and/or you're exceeding V-speeds for each.

[@leftbrosfpv]

Good video

[@DirtFlyer]

Great video. When I was getting checked out in a super cub we spent a day doing lots of forward slips so I could get accustomed to the increased rudder authority that plane provided, compared to the cessnas I had been usually flying. When the instructor demonstrated forward slips he would take the speed down to near stall speed in the forward slip and kept the nose right on the horizon. I found that somewhat alarming, because I knew that a stall in uncoordinated flight could easily lead to a spin. A very bad deal at low altitude. I asked him about it a few times, but he insisted that was how forward slips should be flown. When he handed the controls to me, I did what I knew was right, and lowered the nose a bit when the speed dropped well below approach speed. He kept admonishing me for that, and after that flight I switched instructors. In hindsight I probably should have complained to management about that too. He was making a pretty serious mistake in his instructions that had a real possibility of getting someone killed.

[@GZA036]

Here’s what Bill Thompson, former Manager of Flight Test & Aerodynamics at Cessna, had to say about the issue of slipping with full flaps in the 172 (Cessna - Wings for The World, by William D. Thompson, Maverick Press, 1991, p. 41): With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner’s manuals under “Landings” reading “Slips should be avoided with flap settings greater than 30 deg. due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings”. Since wing-low drift correction in crosswind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative “upwash increment” from the upturned aileron in slipping flight. Although not stated in the owner’s manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students. This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counteract it if it occurs close to the ground. You'll notice that beginning with the 1972 model year ('73 for European-built models) 172s have a larger dorsal fin. This apparently eliminated the "pitch-down" problem. *However, there is also an unrelated, more benign phenomenon that Thompson described in newer models in full-flap slips: “a mild pitch ‘pumping’ motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed.” This really isn't a problem and it's not limited to Cessnas -- my Sport Cub does it, as well, and it doesn't keep me from slipping with full flaps in either airplane. So although the 172L’s larger dorsal apparently solved the pitch-down issue, they kept the cautionary note in the POH because of the latter phenomenon. Unfortunately Cessna contributed to the “end of the world” fear of slips with flaps, by not explaining the pitch-down phenomenon in the manuals; and in fact, many earlier C-172 manuals expressly said that slips with full flap were prohibited. I rummaged through my collection of old Cessna owners manuals: 1958 C-172: “prohibited” 1959 C-175: “prohibited” 1966 C-172F: “prohibited” 1972 C-172L (first year of the big dorsal): “should be avoided” The manuals and TCDS for these older models have been revised since then, and there is now no legal prohibition against slips with flaps -- but that’s what a lot of us old-timers read back then and remember. And some further clarification: The pitch-down that might occur with flap-down slips in Cessnas is not from "elevator blanking." Cessna's aerodynamicist and test pilot said, "The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative 'upwash increment' from the upturned aileron in slipping flight." In other words, in extreme slip conditions some of the upwash from the upturned aileron on the lowered wing might hit the horizontal stabilizer. Flaps cause downwash on the horizontal stabilizer -- that's why retrimming is necessary when flaps are extended. When some of that flap downwash is replaced by upwash from the aileron, there is very suddenly too much nose-down trim, and the nose pitches down. "Elevator blanking" makes it sound as if the elevators lose effectiveness, and that's not what is happening. The pitch-down is not a consistent phenomenon in 172s; Cessna test pilots found it "elusive and sometimes hard to duplicate." And apparently the larger dorsal fin from 1972 onward prevents the 172 from yawing far enough in a slip to allow aileron upwash to hit the tail, so the issue is moot. It's interesting that the old (pre-1972) C-172 owners handbooks (which do not carry the force of law) said slips with full flaps were "prohibited" -- while the current version of the TCDS (which is the "law") only calls for placards saying "Avoid slips with flaps down" (172 thru 172E) or "Avoid slips with flaps extended" (172F thru 172N). The old "prohibited" language is nowhere to be found. There is no caution against slips with flaps in the 172P and newer, in which maximum flap extension is reduced to thirty degrees.

[@Mrfrenchdeux]

This is a good explanation. Thanks.

[@damondeluca]

Great video. Thank you!!

[@alexcanaviri13]

it's very interesting and well explained thanks

[@NativeEarthlingAI]

Great job

[@mrthomaslaux1]

Is that many hours on an engine too much or its still good to buy for cross country purposes?

[@AltitudeAerials]

Thanks for this Gary! Love your straight-to-the-point attitude and not mucking around the main topic of the video. Are you going to have a side slip video coming up too? Thanks again!

[@GarryWing]

Altitude Aerials I did a Crosswind Landings video (1/2014) that covered the side slip...

[@AltitudeAerials]

Just watched that, thanks for pointing that out gary!

[@rdlez]

Gary, I'm taking lessons in A Tecnam P98 Super Echo and I was wondering if you have any videos on fly that aircraft or one similar? Thanks, Rich

[@danielwatkins6917]

love your videos Gary keep em coming! question; do you ever do seminars???

[@AlexTheG9009]

Great video.

[@CaptCardoso]

Great video. Quick question tho, whats the procedure to reduce your rate of descent as soon as you have lost the required amount of altitude?

[@ryanhamlin6177]

Afolabi Cardoso stop cross controlling and add touch of power.

[@orangebetsy]

Just a beginner here. Coming in at 55 KIAS, what is the stall speed in this situation? is it higher than it would be flyin straight?

[@TheFlyingZulu]

55 kts indicated can be quite low when being so uncoordinated... I personally keep it 65 or higher. 3:55

[@mymyrrah]

what do you fly?

[@hulado]

Garry when i was a student pilot many years ago i read about cross controls on final in a flying mag and tried it several times short and steep. didnt matter which way but full rudder and full opposite aileron. was strange to be looking out the side window at the runway centerline. dropping like a rock. come to think of it i think i brought the nose up a tich just before i started the manuver. was easy to recover from. is this dangerous?

[@GarryWing]

Dangerous? Slip: No / Skid: Yes! You're more likely to induce a spin from Straight/Level than you are in a Slip. Not sure about you "bringing up the nose a bit"; the point of uncoordinated (slipping) flight is creating drag that allows you to LOWER the nose, without picking up airspeed. As I've said and demonstrated elsewhere, I can see no reason to ever knowingly Skid an airplane.

[@MrAlwaysBlue]

Sounds a useful manoeuvre. Been practicing on simulator before trying for real.

[@TheCapTan]

So it's ok to slip with flaps. I have heard mixed input from different instructors. Also spins are rare with slips correct?

[@GarryWing]

KTS Check the POH. Cessna 172N is placarded to avoid slips w/ flaps (but not prohibited); C-172SP discourages "steep slips" with > 20-degrees flaps. Mainly results in oscillation of elevator being blanked by flaps while uncoordinated. And slips are less likely to produce a spin than straight/level flight, according to Rich Stowell, as yaw is less-coupled w/ AOA in a slip than in coordinated flight.

[@WizzRacing]

+Garry Wing I actually practiced this with large scale remote control airplanes using the C-172. You can actually see the whole process doesn't produce a spin unless you force one to happen. The dirty air from the flaps causes the elevator to respond slower which is why air speed should be watched while doing this. I was told if you're not sure go around. It takes less time then having to clean up an accident. Good Advise to practice this. As you will be checked on this anyways.

[@nuclearnyanboi]

What do we do when we have asymmetric flaps?

[@nightwaves3203]

It's probably a good idea to practice high speed slips. Having tower announce expedite landing and hold short of the crossing runway for a landing DC-9 was funny. Must of had tower thinking his time perception and vision was off. I was glad when the plane finally started braking from the extreme slips during forward and turns dropping in.

[@agassidr]

Thank you Sir...

[@lkorn9150]

Not sure if I'd be comfortable slipping a 172 with full flaps especially at 55 kts on short final. Sounds sketchy to me.

[@GarryWing]

Get some short-field (over obstacles) training. You'll learn to become comfortable slipping with flaps at approach speed to get to an 1,100' strip over a tree line. Not sure what the concern is; as long as you don't exceed critical AOA (descending 1,000+ FPM, in this case) you're not going to stall, right.....?

[@lkorn9150]

Garry Wing I suppose in that case I could understand the need to use full flaps in a slip, but I was under the impression that the Cessna's POH said slipping with full flaps is not recommended because airflow disruption from the flaps over the elevator could potentially tail plane stall you.

[@ramflyer1899]

The concern is that the horizontal stabilizer / elevator gets washed out by the flaps. It does feel like someone is jumping up and down on the tail. Strange but not an issue. The placard on a 172 says slips not recommended but also not prohibited.

[@daffidavit]

I've been doing it for 50 years. Still here, although I sometimes wonder, how, but for the Grace of God, for some other dumb things I've inadvertently done. But slipping with full flaps is ok in C-150/152s and 172/182's. Remember, the pitot tube will not be getting a direct airflow and indicated airspeed will be inaccurate during the slip. DPA, CFIA

[@GZA036]

@@lkorn9150 There is no possibility of tail plane stall, that was fixed in 1972. There is a benign elevator oscillation, and no - it's not because the elevator is "washed out" by the flaps... Here’s what Bill Thompson, former Manager of Flight Test & Aerodynamics at Cessna, had to say about the issue of slipping with full flaps in the 172 (Cessna - Wings for The World, by William D. Thompson, Maverick Press, 1991, p. 41): With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner’s manuals under “Landings” reading “Slips should be avoided with flap settings greater than 30 deg. due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings”. Since wing-low drift correction in crosswind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative “upwash increment” from the upturned aileron in slipping flight. Although not stated in the owner’s manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students. This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counteract it if it occurs close to the ground. You'll notice that beginning with the 1972 model year ('73 for European-built models) 172s have a larger dorsal fin. This apparently eliminated the "pitch-down" problem. *However, there is also an unrelated, more benign phenomenon that Thompson described in newer models in full-flap slips: “a mild pitch ‘pumping’ motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed.” This really isn't a problem and it's not limited to Cessnas -- my Sport Cub does it, as well, and it doesn't keep me from slipping with full flaps in either airplane. So although the 172L’s larger dorsal apparently solved the pitch-down issue, they kept the cautionary note in the POH because of the latter phenomenon. Unfortunately Cessna contributed to the “end of the world” fear of slips with flaps, by not explaining the pitch-down phenomenon in the manuals; and in fact, many earlier C-172 manuals expressly said that slips with full flap were prohibited. I rummaged through my collection of old Cessna owners manuals: 1958 C-172: “prohibited” 1959 C-175: “prohibited” 1966 C-172F: “prohibited” 1972 C-172L (first year of the big dorsal): “should be avoided” The manuals and TCDS for these older models have been revised since then, and there is now no legal prohibition against slips with flaps -- but that’s what a lot of us old-timers read back then and remember. And some further clarification: The pitch-down that might occur with flap-down slips in Cessnas is not from "elevator blanking." Cessna's aerodynamicist and test pilot said, "The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative 'upwash increment' from the upturned aileron in slipping flight." In other words, in extreme slip conditions some of the upwash from the upturned aileron on the lowered wing might hit the horizontal stabilizer. Flaps cause downwash on the horizontal stabilizer -- that's why retrimming is necessary when flaps are extended. When some of that flap downwash is replaced by upwash from the aileron, there is very suddenly too much nose-down trim, and the nose pitches down. "Elevator blanking" makes it sound as if the elevators lose effectiveness, and that's not what is happening. The pitch-down is not a consistent phenomenon in 172s; Cessna test pilots found it "elusive and sometimes hard to duplicate." And apparently the larger dorsal fin from 1972 onward prevents the 172 from yawing far enough in a slip to allow aileron upwash to hit the tail, so the issue is moot. It's interesting that the old (pre-1972) C-172 owners handbooks (which do not carry the force of law) said slips with full flaps were "prohibited" -- while the current version of the TCDS (which is the "law") only calls for placards saying "Avoid slips with flaps down" (172 thru 172E) or "Avoid slips with flaps extended" (172F thru 172N). The old "prohibited" language is nowhere to be found. There is no caution against slips with flaps in the 172P and newer, in which maximum flap extension is reduced to thirty degrees.

[@HasithaErangaMudalige]

Thank you :)

[@jasonmonson2156]

With a forward slip is carb heat required?

[@GarryWing]

You generally apply carburetor heat prior to reducing power below the green arc on the Tachometer, irrespective of what maneuver you're performing. As you'd normally not slip a plane with cruise power (like using the brakes on your car while stepping on the gas), the short answer is "yes". Consult your airplane's POH; it will give specific guidance for use of carb heat.

[@jasonmonson2156]

Ok. Appreciate it !

[@kentwilliams4152]

I can see why it is a good skill in an aircraft without flaps.

[@otissumnerbrown]

To do this safely, it would be good to "spin" the plane. This is aerobatic training, and shows what can happen if you "push" slips to hard. This type of training - was a life-saver for me. Recommended.

[@GarryWing]

Otis Brown You're more likely to spin from straight-and-level flight than you are in a slip...

[@nickmanning5455]

+Garry Wing what makes you say that?

[@otissumnerbrown]

+Garry Wing From the book, "Stick and Rudder", it is clear that making a left hand turn, you have left rudder, and are slowing down. This is not "forward slip", but it is the loss of airspeed, and causes the plane to "break" into almost inverted flight - close to ground. This is why I believe that pilots should be taught the "sense" of spin entry. This type of aerobatic training - saved my life.

[@GarryWing]

+Nicholas Manning *Aerodynamics.* _Yaw and Roll are as far from coupled as possible during a slip._ (Page 335 from Rich Stowell's excellent _Stall/Spin Awareness_ book). Not enough rudder authority in a Cessna 172 to do an 'over the top' spin from a slip... in something like an Extra? Sure, but I would assume if you were flying an Extra you would already know all this stuff.

[@GarryWing]

+Otis Brown Otis- Don't think in terms of left/right; it's only confusing you. Think of HIGH rudder (slip) or LOW rudder (skid). Of course I wasn't using LEFT rudder in a LEFT turn as I demonstrated SLIPS in a video, c'mon!

[@lw216316]

a view from the ground would be nice - an easier / less expensive way to show a view from the ground would be to use a remote control airplane and film it doing the maneuver. I watch videos like this one to learn things that help with my RC flying. With an RC you can really see the effect the controls have when slipping, crabbing, stalling - and if you mess up your heart rate and blood pressure will not go up as much.

[@moonshade99]

Your explanation of difference between forward slip and side slip is confusing, could you explain in simple terms?

[@GarryWing]

Google is your friend when trying to learn much of this. In the time it took to type your comment, you could have googled: "Forward slip vs. Side slip" and your confusion would be alleviated.

[@benree102]

dude, i rode in an airplane and we landed at fallbrook and i was looking to do this because he did a slip because we were high and you landed at fallbrook on the same runway😂

[@cowboycolts]

another reason to use it when your Boeing 767 loses power to all engines an you gotta land at an abandon military base

[@badman1220]

BowlingGlaceon I got that reference, but that disused military base was turned into a drag strip

[@wowferiw8873]

Ok

[@FISHH00KS]

It's very important to slip the airplane when turning base to final. Especially if you're in a steep turn. Slip the airplane right on in there.

[@iRxyanDestinygtaandmoreL]

gimli glider thats why im here i wanna se hoe he did it

[@ulas9085]

It's forbidden to slip a Cessna with flaps

[@GarryWing]

+Ulas Akkaya _Huh?_ How do you land in a crosswind? (I mean, other than slamming it on with the wheels headed toward the weeds?)

[@katherinebeale6840]

+Ulas Akkaya - POH states "Not Recommended with Full Flaps", which is a far cry from "Forbidden".

[@japanese6337]

Do you think that the Earth is flat?

[@GarryWing]

As far as I can see... yes.

[@japanese6337]

Cool

[@carpenterfamily6198]

New guy question, when slipping should the Vertical Speed indicator stay w/in +/-10 ?

[@justinlittle6239]

Great video, thank you.