Side slipping (video)

[Old Koreelah]

...Not so Lyell, but always read the POH. The Citabria and Auster slip beautifully with flap down. It just gives an extra dimension to sink rate

(Lyle) David I often slip without flaps. I would consult the POH if I could find one, but I doubt it would help; the standard D9 didn't have flaps. My little "D-918" is so heavily modified that I rely on the experience of the broader flying community.

 

 

[David Isaac]

(Lyle) David I often slip without flaps. I would consult the POH if I could find one, but I doubt it would help; the standard D9 didn't have flaps. My little "D-918" is so heavily modified that I rely on the experience of the broader flying community.

Yes well I wouldn't slip a modified aircraft on approach if flaps had been experimentally added, I'd maybe try it at plenty of altitude wearing a chute ... you are almost in test pilot mode doing that with modified aircraft.

DJP has just pointed me to the 172N POH which states "Avoid slips with flaps extended" which I have just found under 'Placards'; interesting there is no other detail on slipping in the limitations section like there is for spinning etc. I had it demonstrated by my instructor who let me do it to show me it was a waste of time with 40 out. I must admit I never experienced any buffet of any kind but certainly ran out of rudder and the slip was more of a skid when compared to what I have done in Cubs, Citabrias, Drifters and Austers.

 

 

[dutchroll]

I don't have a problem with sideslipping in general, but I do have a problem with the way it's sometimes applied.

 

My main issue is that too many pilots use unplanned sideslipping to attempt to correct an unstable approach when they had the opportunity to correct it earlier, and really should just go around and try it again. It can also generate high rates of descent close to the ground under those circumstances. There's a degree of "flippancy", for want of a better term, about side-slipping which it does not warrant.

 

In the Cessna 172, Bill Thompson who was the Manager of Flight Tests and Aerodynamics at Cessna stated in his 1991 book:

 

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”.

 

There appears to be a fair bit of contempt for this from quite a number of pilots on some of the Cessna forums who've all done better and sideslipped the Cessna with full flap. After all, what would the guy who was a test pilot for 28 years and the flight test and aerodynamics manager at Cessna know, compared to a 200 hour private pilot?

 

 

[Old Koreelah]

Thanks fellas, that's good enough for me. Although my aircraft has a different configuration, I'll continue to leave the flap closed while slipping. I'm not a test pilot.

 

 

[aro]

Bill Thompson who was the Manager of Flight Tests and Aerodynamics at Cessna stated in his 1991 book:

You missed the continuation:

 

When the larger dorsal fin was adopted in the 1972 C-172L, this sideslip pitch phenomenon was eliminated, but the cautionary placard was retained.

Your quote only applies to pre-1972 aircraft. Even then, given a choice of a possible uncomfortable pitch down and bending the airframe I would risk a slip.

 

All I know from experience under instruction is that side slipping a 150 or 172 with 40 down is a waste of time and diving is more effective.

Weight makes a big difference in that type of maneuver. I suspect it wouldn't be at all difficult to exceed flap limits in a later model 172 with only 30 degree flaps when fully loaded. There are also many aircraft with low flap limits so it's not a good habit to teach without some consideration for the specific model.

 

 

[eightyknots]

I've posted this elsewhere here, but this seems like the right place. Love it!

That is a pretty wild landing. There is the old adage "There are old pilots and bold pilots but there are no old, bold pilots".

 

I wonder if Ernst Udet ever became old?

 

 

[IBob]

That is a pretty wild landing. There is the old adage "There are old pilots and bold pilots but there are no old, bold pilots".I wonder if Ernst Udet ever became old?

No. But it wasn't the flying that killed him:

 

Ernst Udet - Wikipedia, the free encyclopedia

 

 

[David Isaac]

Your quote only applies to pre-1972 aircraft. Even then, given a choice of a possible uncomfortable pitch down and bending the airframe I would risk a slip.

Where is the risk? But you are wasting your time if you have 40 of flap to use, just dive the bastard, easy to do without exceeding white arc.

 

 

 

Weight makes a big difference in that type of maneuver. I suspect it wouldn't be at all difficult to exceed flap limits in a later model 172 with only 30 degree flaps when fully loaded. There are also many aircraft with low flap limits so it's not a good habit to teach without some consideration for the specific model.

Sure but a 30 degree 172 might just slip, but I haven't tried it and white arc speed rules apply no matter how you fly. The Auster has a 56 KIAS flap limit speed, gotta be careful with those old girls, but they slip beautifully anyway without flaps. After all they are just a bigger faster Cub.

[facthunter]

If a plane has a characteristic like that, you would want to be careful in crosswind situations, mainly landings where similar cross controls might be achieved even if not for long periods. From recollection with the older models (C-182) Vfe flap 40 could be exceeded in turbulence. This resulted in buckling being evident on the upper wing surface from flap track loads which I have seen. It became part of my standard pre flight inspection to drop flaps and have a pretty good look on the walk around. Where 40 was available it's pretty effective, and I'm a bit with David here. You can get the beastie down pretty effectively. If it's gusty and x/wind critical I probably wouldn't use 40 flap anyhow. Going around from full flap was something done carefully anyhow. So much trim change with full power applied. Nev

 

 

[dutchroll]

Your quote only applies to pre-1972 aircraft. Even then, given a choice of a possible uncomfortable pitch down and bending the airframe I would risk a slip.

Except in an emergency situation, in which case all bets are off and you do whatever is necessary, under what circumstances would you have a choice between "bending the airframe" and sideslipping it in?

 

 

[eightyknots]

No. But it wasn't the flying that killed him:Ernst Udet - Wikipedia, the free encyclopedia

Very interesting article!

 

 

[aro]

Except in an emergency situation, in which case all bets are off and you do whatever is necessary, under what circumstances would you have a choice between "bending the airframe" and sideslipping it in?

Why do you exclude an emergency situation? That's exactly the situation where it's most likely to happen. Any normal situation you would go around rather than slip or dive at the top of the white arc. If you have an engine failure & are high and fast with a limited landing area - that is when you will have to make the choice.

 

Easy to say all bets are off and do whatever is necessary, but if you exceed Vfe and one flap pushrod gives up the ghost all bets really will be off. Better to sideslip and have elevator buffet or pitch instability than asymmetric flaps at 85+ knots is my theory.

 

 

[facthunter]

Flap asymmetry doesn't get mentioned much in the U/L game. You are certainly going to notice it if it happens, and you have little time to react to recover the situation. Nev

 

 

[dutchroll]

I guess I'm saying that would it not be better to devote more time to judging the approach better, rather than a last second fix by slipping it in?

 

That's not to say "don't ever teach it as a last resort" but I sometimes get this feeling that people see it as some sort of cure-all. "Yeah got too high on this glide approach, but easy fixed, just slip it in like I normally do when I'm too high on a glide approach!" That's an absurd distraction from addressing the root problem.

 

What about your positioning for the selected landing area? Was there a better option? Did you make your key points? How was your speed maintenance? Did you turn at the right position? Could you have judged your flap selection better?

 

If you're going to slip it close to the ground and get that descent rate right up until the last second, you're setting yourself up to bend it one day anyway. I mean, go ahead and roll the dice. My preference would be to practice it higher, and maybe see it once or twice closer to the ground to know it can be done. If anyone wants to regularly practice it on late approach, ultimately I don't care. Just my opinion based on not liking deliberately generating high sink rates right near the ground.

 

 

[facthunter]

A higher sink rate makes things more critical for sure. Slipping to the flare as I've commented on before needs plenty of recent practice. The ability to do this would be most advantageous on an tree bordered outlanding or small field. It's a better view over the nose, (alongside actually) in a biplane. Plenty of Vintage planes don't have flaps so it's par for the course then. Learn to slip properly. Nev

 

 

[David Isaac]

I guess I'm saying that would it not be better to devote more time to judging the approach better, rather than a last second fix by slipping it in?That's not to say "don't ever teach it as a last resort" but I sometimes get this feeling that people see it as some sort of cure-all. "Yeah got too high on this glide approach, but easy fixed, just slip it in like I normally do when I'm too high on a glide approach!" That's an absurd distraction from addressing the root problem.

I understand what you are saying Dutchy, but I frequently deliberately arrive high just so I can practice side slipping (with and without flaps) and I love it. It is a good maneuver to practice and if you have a flapless machine, it is a normal approach technique. But then again I have flown a few vintage birds and rag & tubes in my time.

[dutchroll]

I do have a flapless machine. The only reason I use a very mild sideslip is so I can see out the front because there's no forward visibility over the nose in a normal approach attitude. My sideslip is compensated with power to maintain a normal descent rate.

 

Or if there's crosswind, side-slipping is a valid technique (again compensated with power to maintain a normal descent).

 

Normal technique on final approach in any aircraft to correct the approach path is to use a combination of power and attitude and to do it earlier rather than later.

 

 

[facthunter]

There's a bit of an aversion to powered approaches in RAAus circles, with a fair emphasis on being able to glide to the field in the event of a power loss. I don't think this is appropriate in gusty conditions as power is very useful in maintaining a more precise slope/airspeed situation and aids more effective rudder and elevator response. I have my own views on this but I'm pointing out a common view that won't disappear quickly and has some advantages and some regard it as policy. Nev

 

 

[dutchroll]

Perhaps an amalgamation with Gliding Australia is on the cards soon?

 

 

[facthunter]

I wouldn't think so . I'm telling you like it is , and what a lot think. I'm only the messenger. If I'm testing a New or unproven engine I behave a bit that way till it's sorted. If I'm departing Mt Hotham A circling climb till I can glide to more "friendly" terrain or return is the procedure. Same logic. Nev