Backcountry Pilot

[Zzz]

Split from the "MAF Wheel Landing Technique" thread. Here, it starts out with me getting confused and incorrectly describing the results of a stall in a skidding or slipping condition. I thought I knew what a Moose stall was!
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Skids spin and flip the inside wing over the top. Slips...just keep on slipping.

[Supercubber offline]

Zane,

That's not exactly right. A classic example of a skid is when a pilot overshoots the centerline of the runway on the base to final leg turn and tries to bring it back center with excessive rudder in the direction of the turn. If you stall in a skid the inside wing gives up and tucks under into a spin, not over the top.

If you stall in a slip your inside wing will come up and over the top into a spin because your outside wing has stalled while the inside wing is still flying.

Remember the wing opposite the ball will always stall first.

[punkin170b offline]

A good way to remember is:
A skid is "too much" rudder for the amount of bank.
A slip is "not enough" rudder for he amount of bank.

Both slips and skids are uncoordinated flight, right? A stall close to the ground in either condition may/may not produce a spin, but even if it does, it won't matter which wing goes under/over. They will both result in a very sudden and unacceptable loss of altitude...

It is DEFINITELY possible to produce a very ugly stall from a slipping condition. Go up and try it at a safe altitude...

M

[Supercubber offline]

Close to the ground I will take a stall from a slip anyday compared to a stall from a skid. At least you have a fighting chance in a slip stall.

A skid stall close to the ground and your pretty much dead whatever you try to do. When the wing tucks under in a skid stall, most people try to bring it back with full opposite aileron which only makes it worse.

[punkin170b offline]

I guess all I can say is; close to the ground, slipping, skidding, or coordinated: I choose NOT to stall.

M

[hotrod180 offline]

Why all this discussion? Just don't stall the airplane! Seems like a no-brainer to me.
Anyone contemplating back-country flying should already have gone out & done some stalls to determine the stall speed in various configurations & at different weights, to come up with the speeds to use for various scenario's: standard approach (1.3 x stall), short-field approach (1.1-1.2 X stall),loitering/elk-watching,maneuvering thru obstacles, etc. Most of our airplanes give plenty of warning before they stall, IF your head isn't up and locked.
I've found that in my airplane, I can lose more altitude quicker just by pulling the nose up & getting slow (5-10 mph below "reference" approach speed) than by doing a big slip. Don't have to worry about uncoordinated flight then, inaccurate ASI readings, or "feeling" the slipstream to judge airspeed. Makes for a good short field approach too, even when you're not too high-- come in high, get slow to develop a big sink rate, and just add power (as needed) to reduce the sink rate when necesary. Better than dragging it in real flat, too-- if the engine quits, just push the nose back down, gain some airspeed (back to best glide), and miraculously the glideslope flattens out again & you can still make the runway.
A quote comes to mind with regards to moose stalls, etc- "keep a little airspeed in the bank". (get it?)

Eric

[Yellowbelly offline]

I've found that in my airplane, I can lose more altitude quicker just by pulling the nose up & getting slow (5-10 mph below "reference" approach speed) than by doing a big slip.
Eric

Couldn't agree more Eric. I use the "slow-down-to-go-down" method in the Maule to good effect. If you are too high, slowing down gives you extra TIME to disipate that excess altitude, no matter what descent rate you can come up with. There is a point where the Maule starts to glide like an F-102 at the same IAS, but just relaxing a tiny bit of back pressure makes everything come back to normal before touchdown. Usually don't need power to arrest the descent; L/D seems to take care of it.

YB

[mtv offline]

Eric,

I think this sort of started off in the middle of something. The reference to slipping and skidding was, more appropriately related to maneuvering flight close to the ground, not to a straight in landing approach, as you describe.

The deal with a slip is that the roll goes one direction, the yaw goes the other direction. As supercubber notes, a stall/spin out of this configuration really gives you quite a bit of warning and time to fix it before it gets upside down.

A skid, on the other hand, by definition is a roll and a yaw both in the same direction, ie: a yaw-roll couple. A spin, by definition is a yaw-roll couple. Enter one of these close to the ground, and as the man said, you are on your way to a wreck.

There are a few points that need to be made here.

First, the FAA put turns about a point into the private pilot PTS so we'd learn to maneuver our aircraft around a traffic pattern, recognizing the effects of wind. Its just that it takes less time to see the effects of wind in a circle than it does in a full traffic pattern.

Turns about a point were NEVER intended to instruct you how to look at things on the ground, and yet every pilot in the free world who doesn't spend a lot of time close to the ground thinks the way to look at stuff on the ground is to do a turn about a point. This is simply the quickest way to make a small smoking hole there is. Remember, turns about a point in the FAA PTS are done at 800 to 1000 feet, or traffic pattern altitude. You want to look at something on the ground, you're down at 200 or 300 feet. Things are different down there, and Turns About a Point are pretty grim that low.

Better to use a racetrack pattern or a figure eight or even 270s for this purpose.

A little extra speed may or may not help, by the way. Let's say your airplane (a Cessna 170) stalls at 54 mph. So, being a good believer in FAA doctrine, you select 1.3 Vso for your circling maneuver. So, you're going to circle at 70 mph, a good safe speed. But, remember, the load factor doubles at 60 degrees of bank. You're only using 45 degrees of bank, though, so the stall speed of the plane is now, say 62 mph. Now, you encounter a bit of a gust, and by the way, those dang droop wingtips the prior owner installed just blocked out your view of the critter, so you skid the tail around just a bit with rudder to get the tip out of the way. Now, you have slowed to 65 in the gust deceleration, you've increased the bank angle and you have induced a skid. About this time, you encounter your own wake from circling.

BOOM!!!! Under the left wing goes, and you are now the occupant of a small smoking hole.

That is how at least some moose stalls occur, I think.

There are no doubt many other ways to get there, though.

Don't believe it can happen to you? I can show you the grave markers of some good friends who I personally knew as very accomplished pilots, with a lot of flight hours, who died in these things.

Don't believe for a moment that just stacking on a few extra knots will prevent all of these things. It may help, but it won't prevent them completely. They are the result of a lot of factors adding together, just like a lot of aviation things are.

MTV

[Supercubber offline]

Excellent post MTV. When I made the original post here pertaining to the skid/slips it was in response to a previous post that misstated what the results would be in a skid/stall. Didn't mean to ruffle any feathers, but thought a correction should be made.

I think it is very important to know all aspects of your aircrafts performance especially when a person is loading up and heading for the mountains.

As pointed out, down low there are so many distractions it is very easy to fly into a trap that you can't get out of. If you aren't familiar enough with your aircraft to the point you are constantly looking down at the ball to fly coordinated, you have no business scouting things close to the ground.

In certain situations your aircraft can stall at any airspeed, throttle setting or attitude.

[punkin170b offline]

Great stuff, Eric, MTV (money for nuthin'!). Thanks for the elaborations.

One comment on the "slow down to go down" technique. I agree this does work, although not nearly as well in a 170B as it does in a rag-wing 170 or Maule (also known as an "anvil" when the spinny thing stops turning! ) The 170B just has too much wing area. I can't peg the VSI in my airplane that way, but I can in a slip! The "slow down to go down" technique might work better in a 180/182/185 - as it has basically the same wing area as the 170A/B, just heavier wing loading. 180 series Guys?

M

[hotrod180 offline]

MTV, you've definitely made a few good points. When low & slow, I generally try to limit my bank angle to around 30 degrees, & try to stay coordinated. Key word: try. It's easy to slip/skid or let the bank angle steepen when distracted-- like when orbitting a moose! (but around here it's usually an elk.) Guess that's how a lot of them moose stalls happen- distraction.
I generally pull on a notch of flaps when in observation mode, makes for a better slow-speed pitch angle, lower stall speed, and just more comfortable maneuvering.
You make a good case for non-circular orbits when doing aerial recon- the racetrack patterns sound like a good idea. I'll have to keep that in mind the next time I spot an elk herd-- or a nude beach!
Yoyu also make a good point "the result of a lot of factors, just like a lot of aviation things are". I've heard that concept referred to as an event chain or decision chain.

Eric

[Yellowbelly offline]

or Maule (also known as an "anvil" ... ) M

The anvil has some admirable aerodynamic properties:

Very stable on final approach
Touchdown point is very predictable
Impervious to gusts and crosswinds

If only they could do something about the flare.

[speedbump offline]

Anybody in the Phoenix area got a 170 I can fly? I'll take you up in the Pitts in exchange. I've got to see how they fly just so I can make more smart ass remarks on this site.
I've read a number of posts about "moose stalls", and folks always want to make blanket statements about how to avoid them. The problem isn't what pattern you fly or if you're coordinated, the problem is division of attention. I'll bet if people would just keep scanning inside, outside, moose, inside, outside , moose, there would be a lot less problems. There are also moose CFIT accidents, where people fly into the side of a hill cause they forgot it was there. It's all the same problem.
On the whole slip/ skid issue, I recommend finding someone who's competent and doing some real aggravated cross-controlled stalls in your personal plane. Do them both slipping and skidding, and in turns up to 60degrees. Some planes are docile some are nasty, it's important to know what yours will do. It's also good fun.

[punkin170b offline]

Hehehe... I was wondering why it was taking so long to get a reaction! I though that comment slipped thru the cracks somehow. Don't get me wrong, fellas, I like Maules too. And Yellowbelly, your 3 positive characteristics are absolutely true. Maules do those three things better than a 170 - especially if the 170 is light. Speedbump, you can fly my 170 next time I come down to PHX area. See what you can do about getting us Mesa's contract down there, will ya? All this snow in March makes me wanna move back to AZ.

M

[Zzz]

All this snow in March makes me wanna move back to AZ.

Shame on you dude!

[punkin170b offline]

The snow can bomb the hills all year long as far as I'm concerned, but not my driveway or the roads that take me to the airport! I haven't flown (GA) for 3 weeks cuz of the Wx!

M

[Berk offline]

About this time, you encounter your own wake from circling.
That is how at least some moose stalls occur, I think.
MTV

Oh! So that's what that was!
I was rudely surprised to encounter the stall warning horn w/ 10 degrees flaps & 70mph, while circling during a photo flight one day.

Thanks for the well-rounded treatsie on manuvering flight. Berk

[mtv offline]

Speedbump,

The division of attention thing is simply one part of a very complex phenomenon, which sometimes (but not always) results in a loss of control at low level.

It's actually a combination of speed, angle of bank, AOA, distraction, aerodynamics, wake turbulence, mechanical turbulence, and probably ten other things that I haven't mentioned.

You are absolutely correct though, that pilot distraction (division of attention) can be one of the culprits.

This is PRECISELY why I advocate a figure eight or racetrack pattern for looking at things on the ground, though. Think about it, when you are looking out the window at the "moose", you are wings level, unaccelerated flight, not climbing, not diving, plain vanilla flight. The airplane will pretty much take care of itself, and you can devote more attention to the ground.

On the other hand, once you pass the "moose", you are now strictly a pilot, and your only task is to position the airplane for the next pass.

So, instead of dividing your attention between looking out, flying the plane, monitoring for traffic and trees all at the same time, you temporally separate those tasks to the extent possible.

I realize that you can't completely separate these tasks, but the idea is to minimize the workload and simplify the aerodynamics as much as possible when you are the most distracted.

MTV

[Supercubber offline]

Oh! So that's what that was!
I was rudely surprised to encounter the stall warning horn w/ 10 degrees flaps & 70mph, while circling during a photo flight one day.

This brings up another point, your stall actuator is located on one wing or the other. Depending on your configuration of flight and how the actuator is adjusted, it is entirely possible to enter a stall spin without your stall warning going off. The wing with the actuator may actually be flying while you are stalling the wing without the actuator. So I wouldn't put a lot of faith in the stall warning indicator when manuvering low & slow.

When gunning coyotes we always use a figure eight pattern to keep us in clean air. I remember a Citabria that absolutely did not like flying through it's own wake low & slow. The Super Cub is a little more stable in this situation but still prone to upset if your not careful. Has a lot to do with how you trim the tail on the cub.

[speedbump offline]

MTV,
I love a good discussion! First let me say that I agree that a figure eight is usually an easier way to maneuver around an object on the ground. Although I really dislike the notion that there is only one correct way to do anything. The conditions at the moment should dictate the appropriate maneuver, and sometimes it may be a continuous turn. Other times it's best just to fly away. Good judgement is the key to safety, not procedures.
The thing about division of attention only being a factor kind of misses the point. Environmental conditions, aircraft configuration, terrain features, and the list of ten or more things you mentioned in your response are all things a pilot must continuously give attention to prior to, and during a maneuver such as this. If the pilot had properly divided his attention he would have noticed the skid, noticed the decrease in airspeed, and corrected for them. If he doesn't have time to assess these things, then he's performing the wrong maneuver, which is also part of division of attention.
These are pilot induced accidents pure and simple. If the pilot would have created a scenario where his abilities could manage the multiple variables, the accident never would have happened. For some, your figure eight might slow things down enough to accomplish the task safely. For others nothing but level flight is safe, maybe there are pilots out there that can keep track of everything while performing a rolling 360 around the moose. We must have a grasp of our own capabilities, and accept the consequences when we misjudge.
The point I'm making is that we shouldn't espouse any single procedure as safe and another foolish. There are too many types of aircraft, and too many levels of pilot skill for that to have real validity.