C172 short field landings
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try a very low speed approach with full flap. say at about 45kts ias. if you are too high on approach and apply full slide-slip (max rudder)
an instant and complete tail-plane stall with sudden violent nose down pitching moment.
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SAS
I dont blame you, but you obviously haven't done too much short strip bush work have you? Don't knock it until you've tried it.
Think about it too instead of firing all guns at once.
Asymetric flap is pretty uncommon, not that it would pose as much of a problem as during a go around.
The pitching moment is almost unnoticable bacuase you are on the ground before it has time to show, but it would help actually, you are raising the nose further, further increasing AOA and drag.
Remeber when you first learnt to fly that, the aircraft will stall at a higher speed with flaps up, this serves to reason that if you want to stop the thing from flying and not come off the ground again (due to wind gusts, bumps in the strip) than getting rid of the flap is going to have that wing stalled sooner rather than later. Again I stress that because of the reduced lift, there is more weight on the mains giving you better breaking.
Just so you are aware, I'm getting rid of the flap just prior to the wheels touching the ground. I only do this when I need to (short bush strips, heavy loads).
Remember you can get float when you dont want it from gusts of wind too, not just because your speed is too high.
Where I work, your attitude would kill people. I suggest if your are competent enough with your 172 than you try a few experiements with retracting the flap after and just before landing and see what happens.
BTW for short field technique, I use 60kts and 55 short final (in certain consditions).
1M
I dont blame you, but you obviously haven't done too much short strip bush work have you? Don't knock it until you've tried it.
Think about it too instead of firing all guns at once.
Asymetric flap is pretty uncommon, not that it would pose as much of a problem as during a go around.
The pitching moment is almost unnoticable bacuase you are on the ground before it has time to show, but it would help actually, you are raising the nose further, further increasing AOA and drag.
Remeber when you first learnt to fly that, the aircraft will stall at a higher speed with flaps up, this serves to reason that if you want to stop the thing from flying and not come off the ground again (due to wind gusts, bumps in the strip) than getting rid of the flap is going to have that wing stalled sooner rather than later. Again I stress that because of the reduced lift, there is more weight on the mains giving you better breaking.
Just so you are aware, I'm getting rid of the flap just prior to the wheels touching the ground. I only do this when I need to (short bush strips, heavy loads).
Remember you can get float when you dont want it from gusts of wind too, not just because your speed is too high.
Where I work, your attitude would kill people. I suggest if your are competent enough with your 172 than you try a few experiements with retracting the flap after and just before landing and see what happens.
BTW for short field technique, I use 60kts and 55 short final (in certain consditions).
1M
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the N also has 40 degrees available, and they work very well, too !
I've had a look in my check lists, for the short field speeds and found the following (with the caveat that for maximum performance you should refer to the POH for the specific aircraft)
172 models L, M, N, and P
Short field approach, full flap 61KIAS
Normal approach, 20 flap 55 - 65 KIAS*
172 Model R
Short field approach, full flap (30) 62KIAS
Normal approach, full flap 60 - 70 KIAS
172 Model S
Short field approach, full flap (30) 61KIAS
Normal approach, full flap 60 - 70 KIAS
*No, I don't have an explanation as to why the speed range for a normal approach is below the short field approach speed.
Brooklands
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IRRenewal,
Oops! Got words mixed up there, I meant to say ABOVE 
Cheers,
Jack.
Let's be glad it does. Aviation wouldn't exist otherwise. It even produces lift above the stalling AoA.
Cheers,
Jack.
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Brooklands: *No, I don't have an explanation as to why the speed range for a normal approach is below the short field approach speed.
All other GA aircraft I have flown during a short field approach use speeds lower than the Normal Powered Approach speeds.
The short field approach in the 172 feels remarkably like a NPA without the unusually higher nose attitude, high power to arrest rate of decent and lack of flare.
I figured the speed was high to cover accidents caused by screwed up short field landings. Since the Cessna's book landing distances are very short even without the short field technique.
In the S model with a Vs0 = 40Kias. 61 kts is close to a 50% margin. I would assume you could increase the landing performance even at MTOW by reducing the speed below this and still maintain a safe margin above the stall.
However would not be too keen to meddle with speeds decided at certification.
Any ideas?
Last edited by jonathang; 6th Nov 2004 at 01:19.
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Hi 1M,
Nope, my experience in 172's is limited to grass strips in the U.K. as an instructor, rather than as a bush pilot. Very different disciplines!
I can see where you are coming from, but I would definately kick a student up the a**e if they tried lifting flaps with me, rather than getting the speeds right.
If someone is just having difficulty with getting the a/c where they want it in a 'normal' environment, such as a 500m strip here in the U.K, then they need to practise the basics rather than trying out wierd and wonderful techniques, that may have their place in your world, but not for a low hour PPL.
In this situation dumping flap wouldn't help the fundamental problem of too much speed.
I'm very careful of what I suggest to inexperienced people sometimes, since their exuberence can sometimes overcome their (current) skill level. As they get more experienced, then different techniques may become more appropriate, but nothing can ever compare with getting the fundamental skills down pat.
The world of professional flying is very different from what we are describing here. To be honest there are procedures I use in my day job that would lead me to have a fit if I saw a student using something similar.
I'm just wondering, when dropping into a short, dusty, hot and high field whilst fully loaded up, do bush pilots do the calcs before hand? Doing that sort of flying leaves bu**er all space for mistakes or problems, not a situation I want any of my students to find themselves in (or myself for that matter!). A pro bush pilot may take all this in their stride, but should a 100Hr PPL, who maybe flys a couple of hours a month, even contemplate this sort of thing? Horses for courses and all that....
If you have to dump flap to get in somewhere, then IMHO you shouldn't be there in the first place! I assure you that having that attitude will keep you alive alot longer than any "tricks of the trade."
I will try raising the flap after landing, but I bet that it makes stuff all difference in this environment, whilst increasing the workload. Gusts are all part of the game and the speed should relevant to that. 50% of the gust speed added to the Vat.
The whole relationship between lift and drag, weight and braking efficiency is very complex, I don't see that the difference in braking efficiency is relevant, how many people use even 70% of the braking capability? Unless you are right on the edge of locking up, then the improvement is unimportant.
Your experience tells you one thing about this, mine another, I suppose its all about how you look at it.
Nope, my experience in 172's is limited to grass strips in the U.K. as an instructor, rather than as a bush pilot. Very different disciplines!
I can see where you are coming from, but I would definately kick a student up the a**e if they tried lifting flaps with me, rather than getting the speeds right.
If someone is just having difficulty with getting the a/c where they want it in a 'normal' environment, such as a 500m strip here in the U.K, then they need to practise the basics rather than trying out wierd and wonderful techniques, that may have their place in your world, but not for a low hour PPL.
In this situation dumping flap wouldn't help the fundamental problem of too much speed.
I'm very careful of what I suggest to inexperienced people sometimes, since their exuberence can sometimes overcome their (current) skill level. As they get more experienced, then different techniques may become more appropriate, but nothing can ever compare with getting the fundamental skills down pat.
The world of professional flying is very different from what we are describing here. To be honest there are procedures I use in my day job that would lead me to have a fit if I saw a student using something similar.
I'm just wondering, when dropping into a short, dusty, hot and high field whilst fully loaded up, do bush pilots do the calcs before hand? Doing that sort of flying leaves bu**er all space for mistakes or problems, not a situation I want any of my students to find themselves in (or myself for that matter!). A pro bush pilot may take all this in their stride, but should a 100Hr PPL, who maybe flys a couple of hours a month, even contemplate this sort of thing? Horses for courses and all that....
If you have to dump flap to get in somewhere, then IMHO you shouldn't be there in the first place! I assure you that having that attitude will keep you alive alot longer than any "tricks of the trade."
I will try raising the flap after landing, but I bet that it makes stuff all difference in this environment, whilst increasing the workload. Gusts are all part of the game and the speed should relevant to that. 50% of the gust speed added to the Vat.
The whole relationship between lift and drag, weight and braking efficiency is very complex, I don't see that the difference in braking efficiency is relevant, how many people use even 70% of the braking capability? Unless you are right on the edge of locking up, then the improvement is unimportant.
Your experience tells you one thing about this, mine another, I suppose its all about how you look at it.
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Hi SAS
Thanks for your reply. I totally agree with you sir about being careful of what you are teaching your students. It's something I wouldn't be teaching my PPL students either.
Operationally however it is not something we have to be doing to get into the strip however it makes life much easier. This of course as you rightly said is the difference between your and my environment.
But picture a bush strip thats around 3500 ft asl, that is by no means flat, a lot of undualations, has water pooled on it when it rains and any wind can be unpredictable and gusty on a good day. The strip length maybe a little under 500m, not straight and about 10m wide surouned by mountains thousands feet higher. This is a good bush strip. Ideally you want to get on the ground where you have planned (for example just on the other side of a water puddle).
So you put the plane where you want it but are immediatly sent skyward as you ride up a small undualation at 50 odd knots, so again you're airborne with little rudder control, the crosswind now takes you off the side of the narrow runway and into rough tussock and rocks, the thing is sinking again and a go-round is inevitable, so here you are low, slow and weighted, the last thing you want is sink, but hey just to keep you working you get sink, now you are below the strip and down in a river, strugling your guts out to get Vy. This has actually happened to me in a matter of seconds, however I was a passenger and i tell you now, it wazs pretty scary stuff. Shouln't be there, you got that right!
But alas it happend, and you learn from it.
Retracting that flap is gonna keep that thing on the ground, it will ride over the undulations and wont come unstuck and I needn't inslut your intelligence but when the wheels are not on the ground you haven't any breaking performance at all.
Remember generally the TAS is going to be higher than the IAS at altitude too.
if you mean weight and balance than yes, because these are CTO's. A lot of it however comes down to proficiency on A/C and in these environments. Knowing your aircraft and what it can do are very important as with any operation. This type of flying can be very rewarding in its own unique ways.
Kind regards
1M
Thanks for your reply. I totally agree with you sir about being careful of what you are teaching your students. It's something I wouldn't be teaching my PPL students either.
Operationally however it is not something we have to be doing to get into the strip however it makes life much easier. This of course as you rightly said is the difference between your and my environment.
But picture a bush strip thats around 3500 ft asl, that is by no means flat, a lot of undualations, has water pooled on it when it rains and any wind can be unpredictable and gusty on a good day. The strip length maybe a little under 500m, not straight and about 10m wide surouned by mountains thousands feet higher. This is a good bush strip. Ideally you want to get on the ground where you have planned (for example just on the other side of a water puddle).
So you put the plane where you want it but are immediatly sent skyward as you ride up a small undualation at 50 odd knots, so again you're airborne with little rudder control, the crosswind now takes you off the side of the narrow runway and into rough tussock and rocks, the thing is sinking again and a go-round is inevitable, so here you are low, slow and weighted, the last thing you want is sink, but hey just to keep you working you get sink, now you are below the strip and down in a river, strugling your guts out to get Vy. This has actually happened to me in a matter of seconds, however I was a passenger and i tell you now, it wazs pretty scary stuff. Shouln't be there, you got that right!
But alas it happend, and you learn from it.
Retracting that flap is gonna keep that thing on the ground, it will ride over the undulations and wont come unstuck and I needn't inslut your intelligence but when the wheels are not on the ground you haven't any breaking performance at all.
Remember generally the TAS is going to be higher than the IAS at altitude too.
if you mean weight and balance than yes, because these are CTO's. A lot of it however comes down to proficiency on A/C and in these environments. Knowing your aircraft and what it can do are very important as with any operation. This type of flying can be very rewarding in its own unique ways.
Kind regards
1M
