Defn of "Performance Landing" on PPL Skill Test

[fireflybob]

Can anyone tell me the defined method of flying the "Performance Landing" on the PPL Skill Test.

Two schools of thought seem to be prominent. One says fly the approach to achieve Vat of 1.3 VS at the 50 ft point - in other words what is specified in the Flight Manual/POH to achieve the scheduled landing distance.

Other version is to progressively reduce speed to a value below 1.3 Vs to avoid float etc.

Beagle, are you out there?

[BlueLine]

Standards Doc 20 Section 4

If speeds and techniques for a short field landing are quoted in the Flight Manual, or graphs are available for the applicant to extract the figures required, a short field landing may be required; otherwise a precision approach should be flown to Flight Manual speeds. Crosswind limits should be observed.


Appendix 1

Precision Landing (short field landing). Crosswind Landings, if suitable conditions available.

Correct aircraft configuration, approach path and approach speed. Landing area and braking technique. Complete aircraft manoeuvering (circuit) to establish final approach, normal landing configuration. Maintain stable (trimmed) approach to landing, speed and approach path for landing at normal touch down area.

[BEagle]

Err, yes. I take it to mean what we used to term a "Normal powered approch and landing" flown with precise adherance to POH configurations and speeds.

Typical Eurobabble which doesn't really mean anything specific, I'm afraid!

[Hudson]

Either the Vref speed stated in the flight manual for meeting the certification landing length requiremets is safe or is not safe. Obviously the former.

Whether you call it performance landing, a normal landing, or a short field landing - it should all mean the same thing. Fly a typical Boeing and the Vref speeds obtained from its flight manual are, in general aviation terms, the same speeds used for a performance, short field or normal landing.

In the old days, a short field landing -sometimes known as a precautionary landing, was flown at just above the stalling speed power-on. A classic example of a true short field landing was an aircraft carrier landing where the aircraft came in at a terrifying low speed with lots of power and hanging on the prop as often described.

With most of the old propeller driven military types - Mustang, Harvard, Lanacaster, Dakota et al, it was fashionable to arrive over the fence on a short field landing at 10-15 knots less than normal. There were risks associated with this technique - wind gradient, for instance. The vital thing was power on until the very moment of flare. The prop wash saved your skin. In modern types, this meant that the stall warning buzzer was sounding all the way in signifying only knots above the stall.

Except perhaps for certain types of military operations, the true short field landing is rarely used in civilian circles - thank goodness. Don't try it unless you are in current practice because the insurers will leave you for dead if you prang.

From my experience, few flying training schools teach the use of the certified flight manual threshold speeds as normal landing procedure. They see these speeds as practically a Mayday situation.

People seem to forget that the flight manual speeds (call them what you wish -short field - performance etc) have perfectly safe padding already built in. Float will always be there with these speeds if the GA aircraft is flared and held off in order to touch down at point of stall.

Because flying schools decree that additional speed is flown above the already safe flight manual speed in order to make a so called normal approach, the resulting additional float may be considerable. On a limiting field length this extra float could cause problems.

If flying schools would only teach use of the correct flight manual speeds for all landings, then the confusion between so called normal landings and short field or performance landings would vanish. Being taught a bad habit such as adding a few extra knots when not needed, is something that students don't need.

Perhaps the aim of the game should be to have the student touch down at a given spot on the runway from a normal (flight manual) threshold speed. This is exactly what Boeing pilots try for.

[whatunion]

not quite so

1.3 vs is the speed to cross the threshold at 50 feet in normal wind conditions. Common sense should tell you that if you maintain the power setting and change the attitude the speed will reduce further in the descent from 50 ft to the touchdown. if the change to the landing attiude is carried out correctly there will still be enough safe margin above the stall. Speeds are never quoted below 50 ft as there is no point ,you should be looking outside and hoping the stall warner is servicable!

Note some aircraft are already in the landing attitude at 50 ft and only require a power adjustment to settle onto the runway.

Some aircraft do not use 1.3 vs as a threshold speed because of poor aileron response at slow speed, t

not quite so

1.3 vs is the speed to cross the threshold at 50 feet in normal wind conditions. Common sense should tell you that if you maintain the power setting and change the attitude the speed will reduce further in the descent from 50 ft to the touchdown. if the change to the landing attiude is carried out correctly there will still be enough safe margin above the stall. Speeds are never quoted below 50 ft as there is no point ,you should be looking outside and hoping the stall warner is servicable!

Note some aircraft are already in the landing attitude at 50 ft and only require a power adjustment to settle onto the runway.

Some aircraft do not use 1.3 vs as a threshold speed because of poor aileron response at slow speed, the Piper Aztec being an eaxmple.

A performance or short field landing should not have any different threshold speed than any other landing. Its the flap setting and braking tecnique that prodecues the performance or short field landing. Traditionally flying school operations have always added a very generous increment to Vref(threshold speed) to give aproach speed, Vapp, with plenty of margin for error. Short field operations should be conducted to book speeds otherwise book performave cannot be obtained. Approach speed is normally lower becauseof the need to try and maintain constant attitude, and thus speed (1.3VS) earlier out to aid accurate positioning on the runway.

Other points to consider are gusty or strong winds which will need threshold speed increments. Threshold 1.3 i is based on power off stalling speed normally quoted at max landing weight on light a/c. Most short field landing accidents are caused by overspeed at the threshold or deep landings produced by unstable approaches.

not quite so

1.3 vs is the speed to cross the threshold at 50 feet in normal wind conditions. Common sense should tell you that if you maintain the power setting and change the attitude the speed will reduce further in the descent from 50 ft to the touchdown. if the change to the landing attiude is carried out correctly there will still be enough safe margin above the stall. Speeds are never quoted below 50 ft as there is no point ,you should be looking outside and hoping the stall warner is servicable!

Note some aircraft are already in the landing attitude at 50 ft and only require a power adjustment to settle onto the runway.

Some aircraft do not use 1.3 vs as a threshold speed because of poor aileron response at slow speed, the Piper Aztec being an eaxmple.

A performance or short field landing should not have any different threshold speed than any other landing. Its the flap setting and braking tecnique that prodecues the performance or short field landing. Traditionally flying school operations have always added a very generous increment to Vref(threshold speed) to give aproach speed, Vapp, with plenty of margin for error. Short field operations should be conducted to book speeds otherwise book performave cannot be obtained. Approach speed is normally lower becauseof the need to try and maintain constant attitude, and thus speed (1.3VS) earlier out to aid accurate positioning on the runway.

Other points to consider are gusty or strong winds which will need threshold speed increments. Threshold 1.3 i is based on power off stalling speed normally quoted at max landing weight on light a/c. Most short field landing accidents are caused by overspeed at the threshold or deep landings produced by unstable approaches.

i see you also mentioned float.

To prevent float keep the power on for as long as possible past the threshold into the roundout. If you round out as close to the runway as possible and then close the throttle the aircraft should immeadiately sink onto the runway. correct threshold speed and accurate round out are essential

[Hudson]

Whatunion.

I am mystified. I would have thought that it was desirable to touch down as slow as possible - that is why tail-wheel types carry out three-point landings. It is only jet or turbo-prop types that in general are flown on to the runway.

Certainly if carrying out a precautionary landing where minimum ground roll is important - especially on rough ground - you certainly should not be flying it onto the ground with flying speed still there. That is a classic way of not only damaging the nose wheel but an undulation of the landing surface may throw the aircraft back into the air.

Here is an extract from that delightfully written book Elementary Flying Training published by the Air Ministry in 1943.
Page 78.

"How to Hold-Off. Once you have begun the stick movement required for flattening out, you have to go on gently easing the stick back towards you, so that the wheels keep the same distance from the ground.

You have to judge your height above the ground so as to avoid climbing or touching down too soon. Once more, you must look well ahead, and to one side, but this time you are looking in a definate direction at a constantly changing ground. Remember that., although you are trying to keep your wheels just off the ground, the tail is gradually getting nearer to the ground and the nose farther from it.

Throughout this period, keep the pressure gently on the stick, bringing it back towardsyou imperceptably until it is right back, when the aircraft stalls, and your landing is made.
Unquote:

A true short field landing (you are lost and have to get into a paddock), is carried out like a carrier landing - ie approach just above the stall around 1.05Vs using power to give you lift from the slipstream. Cut the power at the flare and float is minimised because the aircraft is already in a tail-down landing attitude and has run out of lift.

The 1.3Vs approach (or, as some term the manoeuvre, a performance landing, short field or precautionary landing,) ensures a safe margin above the power-off stall speed and therefore, if the touch-down speed is at the point of stall, must inevitably involve some float. It is therefore not a true short field landing in the emergency sense.

There is no float if the approach is made at say 1.05 Vs above the stall. Logically it follows that there must be float at 1.3Vs - if the aim is to touch down on the stall as explained in the earlier quote.

If the Regulations do not permit an approach speed below 1.3Vs, then the true short field landing is not attainable. Ask any wartime and immediate post war military or civilian pilot.

I do go on so, don't I? Sorry....

[poteroo]

Performance Landings

I'd always interpreted performance to mean the very shortest that the aircraft could be landed, ie, a short field landing. I'm sure this is how most Australian instructors would.

The contentious area of the short field landing is in how it's done.

Submarine approaches, very flat, with power on, nose up and stall warning blaring, are, unfortunately some instructors' idea of short field. In theory, if you use the threshold as the aiming point, fly 1.3 Vsf down through 50ft, power off and full flap, then flare and hold off to stall - this will be the shortest distance.

However, in real life, there are always obstacles on approach,or the undershoot is rough 'as', or there's turbulent air below the 'top-of-trees' line - so one needs some power on for safety. But that doesn't mean >Vsf on the ASI. That couple hundred RPM allows for better command of rudder and elevator, and, very importantly, prevents engine 'falter' if you really need power in a hurry near the ground.

The real skill in the performance of short field landings is to do a steep approach over obstacles, in a safe configuration and speed, yet touchdown short at near stall. It's a skill that needs a bit more training into PPL's intending to fly in and out of paddocks and short strips in OZ.

Ag pilots, flying piston tailwheel types, use the 'Boeing' approach of holding an 'angle' down to a predetermined touchdown point, yet flying at a speed definitely not with the stall sounding, yet < 1.3Vsf. From this approach, a very abbreviated flare plants the mains on the strip, and you have the crosswind beaten + can see where the rough bits are + can brake carefully as there is weight on the wheels.

As a last resort, the approach can be steepened by a little 'forward slip' applied until you pass the top-of-trees line. Of course, if you fly a turbine, the beta approach technique simplifies the short field approach unbelievably.

Anyway, all the above notwithstanding, in my humble opinion, a performance landing means a short field landing - certainly in Oz.

[whatunion]

Sorry for the delay i have been away earning a living (flying!)

Yes hudson it is desirable to touch down as slowly as possible but you also have to have a safe margin above the stall which is even more desirable and life prolonging. Try doing a power on stall with full flap in your aircraft and then imagine that happening at 50 feet. given the option of running through the upwind hedge at 20 mph or smashing onto the threshold like a brick built ****house i know which i would prefer if push comes to shove.

Usiing a threshold speed with a measured safe increment above the of the stall is the correct way to conduct any landing. you will always get people in the club bar who tell you how they appraoch on the stall warner and can land on a sixpence but you know the connection with old and bold pilots i am sure.

the proffesional approach is to use measured performance that make allowances for suitable error. if you look at the figures in an owners manual they will have most likely been achieved by the best pilot on the best day in the best aircraft eg the manufactures test pilot. these figures would not be approved for public transport operation for instance. they would need to be factored to allow for the worst pilot on the worst day in the worst aircraft. performance tables for instance for pub transport opeartions of a c152 would mean that some runways that some flying schools use would be too short. i am not saying you should use the full factor but you should use a suitable cock up factor for long wet grass, inaccuracy, unfamiliar surroundings, terrain, wind, recency, type famil, etc etc.

so the first requirement is to ensure the a/c will fit into the field you want to land in and get out again. (who remebers the air india constellation that landed at RAF northolt in mistake for heathrow but could only get out on the back of a lorry!) and when i say fit in i mean fit in as a proffesional not a cowboy! just scraping across the threshold hedge on the stall is not the way to operate any aircraft.

there have been one or two comparisons with airliners and light a/c which are not really helpful. as mentioned before performance factoring is very generous and allows for the sort of error that can be made by most human beings of average performance. for instance on the jet i fly thrust reversers are not taken into consideration. we could probably land in half the distance we normally do if we really tried. somebody mentioned landind on a spot, on a light a/c yes but not an airliner. our appraoch is based generally on a 3 deg glidepath which puts you across the landing threshold at 50 feet and onto the touchdown zone which is 300 metres further on, further marks are at 150 metres. on a short runway, say Jersey, we want to be on in the 300 metre zone or by the 150 metres marks after the TDZ at the latest. if not ,we are going around. but again its different on a swept back wing jet, we have lift dumpers which prevent the aircarft from bouncing back into the air so we can sit the a/c on pretty firmly, indeed thats what we are aiming to do, get it on, no float, we also have carbon anti skid brakes which have an amazing affect on landing distance.

the other main difference is that swept back wing a/c stall at a higher incidence so they are on the back of the drag curve and are SPEED UNSTABLE on the last section of the approach. small light a/c are generally never on the back of the drag curve on the approach.

the only jets i have flown which are actually in the landing att at roundout height have leading edge slats which put them at a higher app att. with these you merely take the thrust off in ground effect and they sit on.

getting back to the original question the aim of the exercise is not to produce the shortest landing its to produce a safe short field landing. if i sail over the downwind hedge by a foot on the stall warner, crash it onto the ground and dump all the flap and apply max brakes i will do the shortest landing but if thats your technique i would check out your life assurance and make sure all your affairs are in order!

when i was an instructor i used to draw a diagram of 3 approach paths into a short field i labelled one, dead safe.. one. dead lucky and the last on DEAD and thats the one scraping over the threshold.