Shortfield Tips
Joined: Dec 1998
Posts: 4,282
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From: Escapee from Ultima Thule
The technique specified in the manual in all nosewheel light aircraft I've flown is something like:
* Configure the a/c as required
* Hold the a/c on the brakes while applying full power. Confirm that the correct RPM & MP is achieved.
* After brake release accelerate & rotate at the speed specified in the chart to achieve Vtoss by 50'
* Retract gear & flap as scheduled
* Climb at Vx until clear of obstacles.
If you choose to accelerate beyond the specified speed(s) you will have a reduced t/o performance. It's a fallacy to think that doing so improves take off performance OR is necessary to avoid operating behind the power curve. Unlike jets, light a/c aren't behind the power curve after take-off & during climb out.
If they were then rotating at a faster speed would improve performance unless the limiting obstacle is very close - in which case the manufacturer would want to include such things in the performance chart to maximise their claims for the aircraft.
If you rotate at a lower speed than specified then you risk being behind the power curve & reducing take off performance. Some a/c have sufficient power to do this and still improve the take off performance. You lose handling quality protections & buffers built into the scheduled speeds however.
There are considerations & techniques that can be used that are outside the manufacturer's manual but try explaining to the insurers & the CAA if you stuff it up & damage the a/c...
* Configure the a/c as required
* Hold the a/c on the brakes while applying full power. Confirm that the correct RPM & MP is achieved.
* After brake release accelerate & rotate at the speed specified in the chart to achieve Vtoss by 50'
* Retract gear & flap as scheduled
* Climb at Vx until clear of obstacles.
If you choose to accelerate beyond the specified speed(s) you will have a reduced t/o performance. It's a fallacy to think that doing so improves take off performance OR is necessary to avoid operating behind the power curve. Unlike jets, light a/c aren't behind the power curve after take-off & during climb out.
If they were then rotating at a faster speed would improve performance unless the limiting obstacle is very close - in which case the manufacturer would want to include such things in the performance chart to maximise their claims for the aircraft.
If you rotate at a lower speed than specified then you risk being behind the power curve & reducing take off performance. Some a/c have sufficient power to do this and still improve the take off performance. You lose handling quality protections & buffers built into the scheduled speeds however.
There are considerations & techniques that can be used that are outside the manufacturer's manual but try explaining to the insurers & the CAA if you stuff it up & damage the a/c...
Joined: Jun 2002
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From: New South Wales
<<There are considerations & techniques that can be used that are outside the manufacturer's manual but try explaining to the insurers & the CAA if you stuff it up & damage the a/c...>>
If you stuff it up, then it is a case of whatever you were actually doing you say "I was flying by the book, M'lud." You're hardly likely to say "Yes, I rotated 10 knots too early / late."
Of course, if the aircraft was overweight / out of CG that won't wash!
QDM
If you stuff it up, then it is a case of whatever you were actually doing you say "I was flying by the book, M'lud." You're hardly likely to say "Yes, I rotated 10 knots too early / late."
Of course, if the aircraft was overweight / out of CG that won't wash!
QDM
Joined: Aug 2004
Posts: 3,557
Likes: 95
From: moon
ODMQDM you are either not a pilot, or you are dangerously misinformed.
Point (1) GPS groundspeed has absolutely nothing to do with setting yourself up for a good landing, its airspeed thats critical. There is no role for Gps in landing except getting you to the vicinity of the field.
Point (2) The aircraft stall speed increases with the mass of the aircraft, however the Vs quoted in the manual is at max weight
Point (3) Aircraft these days are relatively predictable beasts, refined by geniuses for us idiots to fly. If you stuff it up, then its because you didn't do it by the book - the question then becomes - were you a simple idiot or did you do it deliberately? 10 knots by the way is unforgiveable, 5 knots maybe. By the way, lieing to the authorities is a 'crime involving dishonesty" that at least over here will put your licence, as well as your aviation security identification card (ASIC) renewal in jeopardy
Most schools teach using a reference speed of 1.2 or 1.3 Vs over the fence, however if you are even two or three knots over that in a Cessna you will bounce and float forever.
Best advice is to read the Pilots Operating Handbook and do exactly what it says, otherwise as wiser folks have said, you are your own test pilot.
"bouncing" the aircraft by fiddling with the flaps on takeoff is also a recipe for disaster, you should be concentrating on speed and attitude, not fiddling with a switch or a johansen bar.
do what the manual says no more and no less.
Point (1) GPS groundspeed has absolutely nothing to do with setting yourself up for a good landing, its airspeed thats critical. There is no role for Gps in landing except getting you to the vicinity of the field.
Point (2) The aircraft stall speed increases with the mass of the aircraft, however the Vs quoted in the manual is at max weight
Point (3) Aircraft these days are relatively predictable beasts, refined by geniuses for us idiots to fly. If you stuff it up, then its because you didn't do it by the book - the question then becomes - were you a simple idiot or did you do it deliberately? 10 knots by the way is unforgiveable, 5 knots maybe. By the way, lieing to the authorities is a 'crime involving dishonesty" that at least over here will put your licence, as well as your aviation security identification card (ASIC) renewal in jeopardy
Most schools teach using a reference speed of 1.2 or 1.3 Vs over the fence, however if you are even two or three knots over that in a Cessna you will bounce and float forever.
Best advice is to read the Pilots Operating Handbook and do exactly what it says, otherwise as wiser folks have said, you are your own test pilot.
"bouncing" the aircraft by fiddling with the flaps on takeoff is also a recipe for disaster, you should be concentrating on speed and attitude, not fiddling with a switch or a johansen bar.
do what the manual says no more and no less.
Last edited by Sunfish; 27th March 2006 at 21:18.
Joined: Aug 2000
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From: Norfolk
Sunfish,
you obviously have too much time on your hands - almost a thousand and a half of posts in less than two years....
I saw the flaming that you got on Mil Pilots.
QDMx3 (David, great doctor, great GA pilot) really can fly.
Albeit some of the stuf that you wrote was bonzer, some wasn't, so my suggestion would be; read what was being written in context and then you might want to wind your neck in a bit!
Stik
you obviously have too much time on your hands - almost a thousand and a half of posts in less than two years....
I saw the flaming that you got on Mil Pilots.
QDMx3 (David, great doctor, great GA pilot) really can fly.
Albeit some of the stuf that you wrote was bonzer, some wasn't, so my suggestion would be; read what was being written in context and then you might want to wind your neck in a bit!
Stik
Joined: Jun 2002
Posts: 1,795
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From: New South Wales
Wow, sunfish, you need to chill out a bit mate.
The book can quote whatever stall speed it likes. The indicated speed your particular aircraft stalls at is another matter. In my aircraft, which is a Super Cub, the ASI is not all that reliable down at stall speeds and low speed flying is a lot about how the aircraft 'feels'. That is critically dependent on weight. You ignore the weight of your aircraft in strip flying at your peril, both on the approach and obviously on take-off.
GPS groundspeed on approach is an extremely useful indicator when going into a very short strip and here's someone else who thinks so: http://cubdriver749er.com/
Airspeed 45 knots, groundspeed 45 knots is one thing. Airspeed 45 knots, groundspeed 40 knots is a completely different thing. A glance at the Pilot III on the dash when going into somewhere really short can be a reassuring, wonderful thing: picture looks right, plane feels right, airspeed is right, groundspeed is right, let's keep going.
QDM
The book can quote whatever stall speed it likes. The indicated speed your particular aircraft stalls at is another matter. In my aircraft, which is a Super Cub, the ASI is not all that reliable down at stall speeds and low speed flying is a lot about how the aircraft 'feels'. That is critically dependent on weight. You ignore the weight of your aircraft in strip flying at your peril, both on the approach and obviously on take-off.
GPS groundspeed on approach is an extremely useful indicator when going into a very short strip and here's someone else who thinks so: http://cubdriver749er.com/
Airspeed 45 knots, groundspeed 45 knots is one thing. Airspeed 45 knots, groundspeed 40 knots is a completely different thing. A glance at the Pilot III on the dash when going into somewhere really short can be a reassuring, wonderful thing: picture looks right, plane feels right, airspeed is right, groundspeed is right, let's keep going.
QDM
Joined: Aug 2004
Posts: 3,557
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From: moon
My apologies QDMQDM, I didn't realise you drive a Cub. I am somewhat sensitive to this issue after learning the hard way about what happens when you land a Cessna even a few knots too fast - $1500 insurance excess on a new firewall.
I am now a strong believer in "the book" and practicing with rearward CG and at gross weight as well. One thing I wish for is that performance charts were of a standardised layout - Cessna's seem about the most comprehensive, I also wish that the use of "factored" (ie +15%) and "non factored" charts was discontinued because its confusing. The most incomprehensible charts I've seen are the good old Tobago's.
I am now a strong believer in "the book" and practicing with rearward CG and at gross weight as well. One thing I wish for is that performance charts were of a standardised layout - Cessna's seem about the most comprehensive, I also wish that the use of "factored" (ie +15%) and "non factored" charts was discontinued because its confusing. The most incomprehensible charts I've seen are the good old Tobago's.
Joined: Jan 2005
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From: UK
Originally Posted by ronnie3585
[B]Wombat[B] suggested to lift off and fly in the ground effect to bulid up speed. Would it not be safer to leave the main wheels on the ground (provided you have the runway distance) in case of crosswind, gusts, aborting the take off etc, instead of wallowing around in the ground effect in a low speed/high drag situation?
I know there are many variables e.g. wind, weight, temp & pressure etc but is there one "safer" method for take offs?
I know there are many variables e.g. wind, weight, temp & pressure etc but is there one "safer" method for take offs?
I watched the spat sunfish / QDM and this made me rethink what I told you. In the case of my advice, deploying flap just before rotating into the ground effect is, perhaps, best left until you have a bit more experience. Deploy prior to the roll. In both cases however, get it up into the ground effect at the advised speed. The ability of the aircraft to accelerate when in the ground effect is better than with wheels on the ground. When you reach speed to achieve a positive rate of climb, "rotate" a second time and up you go. Speeds for this in the Archer I fly are 45kts rotate into the ground effect (with 2 stages of flap), increase speed in the straight and level until 65 kts, then climb - still with flap. 500 ft, get rid of flap in stages.
Regarding using a gps to assist with shortfield landings is again, something I would suggest left until you have more experience. Whilst QDM may suggest a "glance" at the gps speed indicator prior to landing, the truth of the matter is that it is one more thing to worry about in what is already a high workload scenario. Leave it until you have a better idea of what you are doing.
When I learned STOL, (and I don't include in learning the five minutes you get during your PPL training) I found a FI who had a good reputation for such things. He started me off on a 600 mtr hard surface and only after I had nailed it (about four attempts) did he take me to the 450 mtr grass strip.
I must confess that I find STOL very very rewarding and get a buzz out of pulling up after a good short field landing. In fact, I am still amazed in how short a distance you can bring an aircraft to a full stop when doing it correctly.
Enjoy
The Wombat
Why do it if it's not fun?
Joined: Jul 2001
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From: Bournemouth
I know there are many variables e.g. wind, weight, temp & pressure etc but is there one "safer" method for take offs?
I learnt to fly on PA28s. My instructor taught me to do a short-field take-off by holding the controls fully back and getting the aircraft airborne asap, then holding it in ground effect. This technique works perfectly well on a PA28. I then tried it on a C152, and found that holding the controls fully back in a C152 results in a sufficient increase in drag that the aircraft will not get airborne. Fortunately, I was on a long runway when I discovered this.
(Incidentally, although I don't fly PA28s all that regularly any more and never into short fields, I don't believe the technique I've described is what the book says, so it's not what I would teach either. But it does demonstrate nicely that a technique which works well on one aircraft type might not work on another.)
FFF
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Joined: Sep 2003
Posts: 480
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From: Retford, UK
Originally Posted by QDMQDMQDM
GPS groundspeed on approach is an extremely useful indicator when going into a very short strip and here's someone else who thinks so: http://cubdriver749er.com/
Joined: Jun 2002
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From: New South Wales
I should have clarified when talking about using GPS groundspeed that most of my landings are in places without windsocks. Most of the time you can assess wind directly from track across the ground, but when the wind is light it is useful to have a GPS groundspeed readout.
QDM
QDM
Joined: Dec 2005
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From: Wellington,NZ
There are many possible variables to take into account, and what might be right on one day, wrong on the next.
Getting it airborne, or at least getting the nosewheel up early, is appropriate for long grass or soft (draggy) surface. Once free of the drag, accelerate as stated above (to what airline pilots, who do this every time they fly) call v2, then climb.This should take only a very few seconds. On a firm strip, that's not necessary, and in fact can be counterproductive, as the increased drag produced by high AoA wings will reduce acceleration.
For landing, as stated above, speed control is all-important. Since there is reduced margin to counter windsheer etc, very wise to become sensitive to that phenomenon, at those low speeds, in a safe environment first. Practise doing minimum-speed steady-rate descents at altitude. Chuck in a turn or two. Learn to feel when the controls get sloppy.(Or sloppier). Most light singles have a mediocre power/weight ratio, so get a negative gust on short final, with a heavy load, at min speed, be very ready to use all the throttle. For this reason, deselect carb heat at least above 100'.
Some lighties (eg the 172) were originally recommended to climb for obstacle clearance at 1.2 Vs; this changed to 1.3 when the certification requirements changed about 20-25 yr ago. My point being that if you are capable, the aeroplane can be made to perform better than the book says it can. I've tried this and it works. (Not recommended in a slab-wing cherokee, though.)
IMO the 182 pilot in the sad video dragged it off the ground prematurely, losing directional control in the process, and was partially stalled for about the next 6 seconds (I reckon the right wing drop after liftoff was the beginning of a wing drop stall) and once clear of the buildings was pretty
much completely stalled.
Best advice, go to a few strips with a good instructor. Get happy in operating into them,in a variety of weight/weather conditions.
What sort of a/c is it you'll be using?
Getting it airborne, or at least getting the nosewheel up early, is appropriate for long grass or soft (draggy) surface. Once free of the drag, accelerate as stated above (to what airline pilots, who do this every time they fly) call v2, then climb.This should take only a very few seconds. On a firm strip, that's not necessary, and in fact can be counterproductive, as the increased drag produced by high AoA wings will reduce acceleration.
For landing, as stated above, speed control is all-important. Since there is reduced margin to counter windsheer etc, very wise to become sensitive to that phenomenon, at those low speeds, in a safe environment first. Practise doing minimum-speed steady-rate descents at altitude. Chuck in a turn or two. Learn to feel when the controls get sloppy.(Or sloppier). Most light singles have a mediocre power/weight ratio, so get a negative gust on short final, with a heavy load, at min speed, be very ready to use all the throttle. For this reason, deselect carb heat at least above 100'.
Some lighties (eg the 172) were originally recommended to climb for obstacle clearance at 1.2 Vs; this changed to 1.3 when the certification requirements changed about 20-25 yr ago. My point being that if you are capable, the aeroplane can be made to perform better than the book says it can. I've tried this and it works. (Not recommended in a slab-wing cherokee, though.)
IMO the 182 pilot in the sad video dragged it off the ground prematurely, losing directional control in the process, and was partially stalled for about the next 6 seconds (I reckon the right wing drop after liftoff was the beginning of a wing drop stall) and once clear of the buildings was pretty
much completely stalled.
Best advice, go to a few strips with a good instructor. Get happy in operating into them,in a variety of weight/weather conditions.
What sort of a/c is it you'll be using?
Thread Starter
Joined: Mar 2005
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From: Ireland.
Just watched the video of the Super Cubs landing on the gravel spits...WOW my jaw is still on the floor!
How do they take off again? Especially the guy that used the river to begin his landing roll!
How do they take off again? Especially the guy that used the river to begin his landing roll!
Thread Starter
Joined: Mar 2005
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From: Ireland.
Originally Posted by markjoy
What sort of a/c is it you'll be using?
Re my previous post, maybe I over estimated a bit when I said I would hold it on the ground for an extra 10kts, its more like five.
I cant but agree about nailing the approach speed. A flying buddy of mine recently left very big skid marks on a very small runway! Was too high and too fast but committed anyway...bloody stupid of him but at least he walked away with no damage done.
Joined: Aug 2000
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From: uk
That's why the best advice is to follow the advice in the book.
However, on grass, I was trained to use 2 stages of flap , rotate at 65 mph and accelerate in ground effect to 74. Many years ago I was taught, in extreme cases, to increase flap to full at 60 mph and then gradually reduce back to 2 stages while accelerating in ground effect. I was also taught this, incidentally, as a rough water technique in a Cub float plane. I have never done it without an instructor in either case.
Can anyone tell me what effect the use of 2 stages of flap is likely to have on take off distance. I still use the normal calculation in the book because its the only one I've got.
Why do it if it's not fun?
Joined: Jul 2001
Posts: 4,782
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From: Bournemouth
Can anyone tell me what effect the use of 2 stages of flap is likely to have on take off distance
However, the extra drag from the flap will reduce climb performance. (Remember that an aircraft climbs because it has more thrust than drag - so any extra drag reduces the amount of thrust available to climb with.) Which is why many aircraft's POH give the option of different amount of flaps depending on whether there are obstacles at the end of the short field (use less flap) or not (use more flap).
The POH in my PA28 says absolutely nothing about short field take off
FFF
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Joined: Jun 2002
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From: New South Wales
All aircraft are different, natch.
In the Super Cub full flap pops you off the deck into ground effect like a cork and then best angle climb is at a truly terrifying 45mph with full flap. What happens if the engine fails in that attitude at 100 feet does not bear thinking about.
QDM
In the Super Cub full flap pops you off the deck into ground effect like a cork and then best angle climb is at a truly terrifying 45mph with full flap. What happens if the engine fails in that attitude at 100 feet does not bear thinking about.
QDM
Joined: Dec 1998
Posts: 4,282
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From: Escapee from Ultima Thule
Pulse1
The book doesn't specifically mention a short field procedure because the one given *is* the short field procedure. The technique specified meets certification criteria about handling qualities, speed buffers etc. Other techniques may get the a/c off the ground earlier - although not necessarily clear an obstacle further along, or may clear a higher obstacle nearby but usually do so at the expense of losing protective speed buffers or reduced handling qualities.
Landing techiques have the same caveats.
Do other techiques work? Sure, but you'd better be very sure of your skills & judgement. My previous job required me to fly into strips as short as 380 m, often in strong turbulence & with obstacles nearby, sometimes at night for air ambulance in rather nasty weather. There are times when operating on the very edge of the performance ability of the a/c will get you in or out, but there will be an increased risk.
The book doesn't specifically mention a short field procedure because the one given *is* the short field procedure. The technique specified meets certification criteria about handling qualities, speed buffers etc. Other techniques may get the a/c off the ground earlier - although not necessarily clear an obstacle further along, or may clear a higher obstacle nearby but usually do so at the expense of losing protective speed buffers or reduced handling qualities.
Landing techiques have the same caveats.
Do other techiques work? Sure, but you'd better be very sure of your skills & judgement. My previous job required me to fly into strips as short as 380 m, often in strong turbulence & with obstacles nearby, sometimes at night for air ambulance in rather nasty weather. There are times when operating on the very edge of the performance ability of the a/c will get you in or out, but there will be an increased risk.
Joined: Aug 2004
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From: moon
For goodness sake, do it by the book!
For what its worth, here is what my Piper Arrow manual says:
"Short field takeoff with an obstaccle or soft field differs slightly........Flaps should be lowered to 25 degrees (second notch)....allow the aircraft to accelerate to 50 to 60 knots depending on aircraft weight and rotate to climb attitude. After breaking ground accelerate to 55 to 65 knots and select gear up. Continue accelrating etc etc.
As for landing, all they say is for short field is full flap and enough power to maintain approach speed (75 knots). Reduce speed during the flareout and contact the ground close to the stalling speed (55 knots). It then goes on to talk about holding the nose wheel off, putting weight on the mains and raising flaps. It then cautions about using partial or no flaps in high wind or crosswind conditions.
From memory the Warrior manual says much the same thing, except I can't remember if you use flaps at all.
Please be very very cautious about instructors who show you a "special" technique unless they are old and very experienced and can explain in detail how and why the procedure works.
Remember that most training is done at well below max weight and what works when your instructor demonstrates it may not work so well when you have Mum and the two kids on board.
Please note that in a Cessna 210 (laminar flow wing) if you rotate too early you will simply traverse the entire length of the airstrip before hitting the fence.
There are a few other interesting ways to get killed, like getting a little too slow on approach and falling out of the back of the drag curve.
As for applying flap during the takeoff roll, you are asking for trouble. One day you will either forget because you are dealing with some other problem, or something will occur just as you reach down for the switch or the bar. I've already nearly been killed by a sticky Cessna flap switch and I don't take my eyes off the runway just to check if the flaps are extending. Things can happen very fast and you don't need to add unnecessarily to your own workload pulling this trick. The gravel strips I've used require all your attention just to keep the aircraft pointing in the right direction and on "centreline"
For goodness sake, use the book!
For what its worth, here is what my Piper Arrow manual says:
"Short field takeoff with an obstaccle or soft field differs slightly........Flaps should be lowered to 25 degrees (second notch)....allow the aircraft to accelerate to 50 to 60 knots depending on aircraft weight and rotate to climb attitude. After breaking ground accelerate to 55 to 65 knots and select gear up. Continue accelrating etc etc.
As for landing, all they say is for short field is full flap and enough power to maintain approach speed (75 knots). Reduce speed during the flareout and contact the ground close to the stalling speed (55 knots). It then goes on to talk about holding the nose wheel off, putting weight on the mains and raising flaps. It then cautions about using partial or no flaps in high wind or crosswind conditions.
From memory the Warrior manual says much the same thing, except I can't remember if you use flaps at all.
Please be very very cautious about instructors who show you a "special" technique unless they are old and very experienced and can explain in detail how and why the procedure works.
Remember that most training is done at well below max weight and what works when your instructor demonstrates it may not work so well when you have Mum and the two kids on board.
Please note that in a Cessna 210 (laminar flow wing) if you rotate too early you will simply traverse the entire length of the airstrip before hitting the fence.
There are a few other interesting ways to get killed, like getting a little too slow on approach and falling out of the back of the drag curve.
As for applying flap during the takeoff roll, you are asking for trouble. One day you will either forget because you are dealing with some other problem, or something will occur just as you reach down for the switch or the bar. I've already nearly been killed by a sticky Cessna flap switch and I don't take my eyes off the runway just to check if the flaps are extending. Things can happen very fast and you don't need to add unnecessarily to your own workload pulling this trick. The gravel strips I've used require all your attention just to keep the aircraft pointing in the right direction and on "centreline"
For goodness sake, use the book!