Takeoff Technique
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Takeoff Technique
Hi all,
I'm currently doing my CPL in Aus, flying 172RG. I've been thinking about this for the last few days. Normal takeoff technique that everyone teaches seems to be power up, check engine green, reaching around 60KIAS rotate and climb out at best rate. Logic being that when your engine quits you have the maximum possible height to work with.
However at the same time we are told to land on the remaining runway or straight ahead if the engine quits. Problem I've noticed is that even when I have a fair bit of runway remaining in front I've gained too much altitude to be able to safely bring the thing down and I'd probably just end up driving the thing into the trees at the end.
Wouldn't it be safer to reach rotate speed, stay low (in ground effect) and wait for the airspeed to pick up to normal cruise. That way if the engine quits you can just put it back down. Seems safer than a nice glide into the trees. Reaching the end of the runway pull up into a climb. Although you are at low altitude you have the benefit of extra speed, ie. extra kinetic energy to be converted into potential (altitude). So if the engine goes right before the end you can still gain height and land straight ahead.
Only a thought, happy to hear it ripped to shreds but try to go easy.
I'm currently doing my CPL in Aus, flying 172RG. I've been thinking about this for the last few days. Normal takeoff technique that everyone teaches seems to be power up, check engine green, reaching around 60KIAS rotate and climb out at best rate. Logic being that when your engine quits you have the maximum possible height to work with.
However at the same time we are told to land on the remaining runway or straight ahead if the engine quits. Problem I've noticed is that even when I have a fair bit of runway remaining in front I've gained too much altitude to be able to safely bring the thing down and I'd probably just end up driving the thing into the trees at the end.
Wouldn't it be safer to reach rotate speed, stay low (in ground effect) and wait for the airspeed to pick up to normal cruise. That way if the engine quits you can just put it back down. Seems safer than a nice glide into the trees. Reaching the end of the runway pull up into a climb. Although you are at low altitude you have the benefit of extra speed, ie. extra kinetic energy to be converted into potential (altitude). So if the engine goes right before the end you can still gain height and land straight ahead.
Only a thought, happy to hear it ripped to shreds but try to go easy.
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Some considerations.
(a) energy-wise through the takeoff, so far as subsequent options are concerned, height beats speed hands down - drag consideration.
(b) if you stay low for speed, you gain little advantage tactically as you then have to get rid of the speed in the forced landing sequence anyway.
(c) the only case which comes to mind where I would like to have a bunch of extra speed when the noise stops is if there is ONE very long row of trees perpendicular to the runway direction and the speed/position is such that one could do a hop and pop over the trees into the next paddock. Generally, though, not a good plan to be fast and low. I guess that Ray Hanna was an exception .. but, for we mere mortals, conservatism is the better plan.
I'd probably just end up driving the thing into the trees at the end
the idea is to steer around/away from the trees .. or, if that's not possible, pick the softest/least undesirable of the available options and fly the aeroplane until it is no longer flyable. Sometimes the options are limited ...
Seems safer than a nice glide into the trees
... hurt is related to the hard bits and energy. Try to miss the hard bits. Energy is related to speed squared. Slow is GOOD if you have to hit the hard bits. Stall speeds are low on singles to give you a reasonable chance of weathering the impact. Indeed, a very early design standard was the selection of 70 mph maximum stall speed (finger in the wind technical basis at the time) for just this reason.
(a) energy-wise through the takeoff, so far as subsequent options are concerned, height beats speed hands down - drag consideration.
(b) if you stay low for speed, you gain little advantage tactically as you then have to get rid of the speed in the forced landing sequence anyway.
(c) the only case which comes to mind where I would like to have a bunch of extra speed when the noise stops is if there is ONE very long row of trees perpendicular to the runway direction and the speed/position is such that one could do a hop and pop over the trees into the next paddock. Generally, though, not a good plan to be fast and low. I guess that Ray Hanna was an exception .. but, for we mere mortals, conservatism is the better plan.
I'd probably just end up driving the thing into the trees at the end
the idea is to steer around/away from the trees .. or, if that's not possible, pick the softest/least undesirable of the available options and fly the aeroplane until it is no longer flyable. Sometimes the options are limited ...
Seems safer than a nice glide into the trees
... hurt is related to the hard bits and energy. Try to miss the hard bits. Energy is related to speed squared. Slow is GOOD if you have to hit the hard bits. Stall speeds are low on singles to give you a reasonable chance of weathering the impact. Indeed, a very early design standard was the selection of 70 mph maximum stall speed (finger in the wind technical basis at the time) for just this reason.
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It's all about energy management.
You are still adding the same amount of power (energy) to the equation - you can either convert that energy to height (potential energy) or convert it to speed (kinetic energy).
If you accelerate in ground effect to say a cruise speed and then the engine quits you still have to stop. If you plonk it on the ground at 120 knots the Dunlops will do bugger all to stop you - the wing will still be generating lift severely limiting braking capacity - and that's the best case if the tyres survive the landing.
Ok you can pull back on the stick to convert some of the kinetic energy to potential energy, but that defeats the purpose of your proposed technique in the first place.
IMHO once obstacle clearance is no longer an issue, accelerating to and climbing at Best Rate will give you the most options if the fan stops. It is a very efficient airspeed - you will lose less energy through drag and will therefore maximise the time before you have to land. In most light singles Vy is reasonably close to the best glide speed as well.
The other advantage with a lower airspeed is that it reduces the radius of turn for the same bank angle, or from the opposite perspective it reduces the amount of bank to required to land in the same area that is not directly in front of you. Once again this will give you more options.
When an engine fails in a SE aircraft the insurance company buys the hull at this point and not when the aircraft is stopped. The aim of the exercise is to maximise the survivability for everyone on board - if the best way to achieve this will result in the aircraft being destroyed so be it. However on the same token putting the aircraft down undamaged will result in everyone surviving uninjured.
One of the big debates is when to retract the gear in a SE aircraft. One theory is to wait until you can no longer land on the remaining runway and stop before retracting the gear. The other theory is to retract the gear as soon as you have positive rate of climb. The advantage of the second method is it gives you a higher rate of climb and therefore more energy in the bank (more time, more options) if the engine stops. OK it increases the risk of landing with the wheels retracted on the runway, but from a survivability perspective very few people are injured in wheels up landings.
JT you beat me to it - but surely climbing at best rate would give you the best chance of clearing the trees wouldn't it?
You are still adding the same amount of power (energy) to the equation - you can either convert that energy to height (potential energy) or convert it to speed (kinetic energy).
If you accelerate in ground effect to say a cruise speed and then the engine quits you still have to stop. If you plonk it on the ground at 120 knots the Dunlops will do bugger all to stop you - the wing will still be generating lift severely limiting braking capacity - and that's the best case if the tyres survive the landing.
Ok you can pull back on the stick to convert some of the kinetic energy to potential energy, but that defeats the purpose of your proposed technique in the first place.
IMHO once obstacle clearance is no longer an issue, accelerating to and climbing at Best Rate will give you the most options if the fan stops. It is a very efficient airspeed - you will lose less energy through drag and will therefore maximise the time before you have to land. In most light singles Vy is reasonably close to the best glide speed as well.
The other advantage with a lower airspeed is that it reduces the radius of turn for the same bank angle, or from the opposite perspective it reduces the amount of bank to required to land in the same area that is not directly in front of you. Once again this will give you more options.
When an engine fails in a SE aircraft the insurance company buys the hull at this point and not when the aircraft is stopped. The aim of the exercise is to maximise the survivability for everyone on board - if the best way to achieve this will result in the aircraft being destroyed so be it. However on the same token putting the aircraft down undamaged will result in everyone surviving uninjured.
One of the big debates is when to retract the gear in a SE aircraft. One theory is to wait until you can no longer land on the remaining runway and stop before retracting the gear. The other theory is to retract the gear as soon as you have positive rate of climb. The advantage of the second method is it gives you a higher rate of climb and therefore more energy in the bank (more time, more options) if the engine stops. OK it increases the risk of landing with the wheels retracted on the runway, but from a survivability perspective very few people are injured in wheels up landings.
JT you beat me to it - but surely climbing at best rate would give you the best chance of clearing the trees wouldn't it?
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but surely climbing at best rate would give you the best chance of clearing the trees wouldn't it?
quite so.
I probably didn't express myself as well as I would have liked to in the previous post ... one of the problems with throwing in throw away lines, I guess.
I can recall Jack Macdonald holding Bob Eastgate's Mustang down at Essendon on several occasions until the last 500ft or so of the runway .. magic stuff, very relevant to military operations in a hot zone, and great to watch (if you had someone standing in front of you then you couldn't see much of it at all).
For the real world likes of the rest of us in C172s and similar stuff ... height is the way to go.
quite so.
I probably didn't express myself as well as I would have liked to in the previous post ... one of the problems with throwing in throw away lines, I guess.
I can recall Jack Macdonald holding Bob Eastgate's Mustang down at Essendon on several occasions until the last 500ft or so of the runway .. magic stuff, very relevant to military operations in a hot zone, and great to watch (if you had someone standing in front of you then you couldn't see much of it at all).
For the real world likes of the rest of us in C172s and similar stuff ... height is the way to go.
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Thanks for the responses guys, much appreciated. I've wondered about the undercarriage straight up business too. I normally leave it down until no runway remaining, unless I'm doing a short field in which case it comes straight up.
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JT,
Correct me if I'm wrong, but the equation with a pure jet would be a bit different - because jets generate thrust not power. I would think that with a higher aircraft speed the engines would add more energy per unit of time. More energy = more time / options.
I think someone killed themselves a number of years ago here in Aus using a technique like this as their regular technique - they didn't push forward quickly enough after the zoom - stalled, spun, crashed and burned.
Correct me if I'm wrong, but the equation with a pure jet would be a bit different - because jets generate thrust not power. I would think that with a higher aircraft speed the engines would add more energy per unit of time. More energy = more time / options.
I think someone killed themselves a number of years ago here in Aus using a technique like this as their regular technique - they didn't push forward quickly enough after the zoom - stalled, spun, crashed and burned.
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but surely climbing at best rate would give you the best chance of clearing the trees wouldn't it?
quite so.
quite so.
Best climb ANGLE will give you the most clearance over a close-in obstacle.
However, especially for a relatively inexperienced pilot, climbing at best angle speed (Vx) will give less stall margin in case of engine failure than will best rate (Vy). Unless the trees are VERY close and your clearance above them VERY small (as in too scary to really want to try), Vy will give you an adequate margin overall.
Remember, crashing into trees straight ahead is preferable to stalling and crashing into the ground in a vain attempt to return to the runway from too low an altitude.
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but the equation with a pure jet would be a bit different
Quite probably - last I looked, the typical profile for time to height was something like
(a) 0.9-ish half loop and roll off the top
(b) transonic acceleration in a shallow dive
(c) from whatever the magic speed is for the Type, zoom to height.
Best climb ANGLE will give you the most clearance over a close-in obstacle
.. granted but largely immaterial for the typical small GA single.
Quite probably - last I looked, the typical profile for time to height was something like
(a) 0.9-ish half loop and roll off the top
(b) transonic acceleration in a shallow dive
(c) from whatever the magic speed is for the Type, zoom to height.
Best climb ANGLE will give you the most clearance over a close-in obstacle
.. granted but largely immaterial for the typical small GA single.
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Best climb ANGLE will give you the most clearance over a close-in obstacle
.. granted but largely immaterial for the typical small GA single.
.. granted but largely immaterial for the typical small GA single.
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Perhaps also worth planning what you are going to do if it doesn't quit but instead goes to a low power or rough running mode. From what I hear that's almost worse than having it stop.
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Intruder,
Logic suggests to me the Vy will give better obstacle clearance over trees following an engine failure for a number of reasons.
Logic suggests to me the Vy will give better obstacle clearance over trees following an engine failure for a number of reasons.
- The aircraft will be higher - meaning it will glide further and longer - creating a larger landing footprint.
- The aircraft will have traveled further - meaning the available landing footprint will be further in front of the aircraft.
- If it is only a partial engine failure Vx and Vy will become closer together - it is far easier to decelerate from Vy to maximise performance than to accelerate from Vx.
- Whilst the aircraft will be lower in the very early part of the climb (due to loss of climb performance due to acceleration) most of that energy would be able to be converted to height anyway.
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Intruder,
Logic suggests to me the Vy will give better obstacle clearance over trees following an engine failure for a number of reasons.
* The aircraft will be higher - meaning it will glide further and longer - creating a larger landing footprint.
* The aircraft will have traveled further - meaning the available landing footprint will be further in front of the aircraft.
* If it is only a partial engine failure Vx and Vy will become closer together - it is far easier to decelerate from Vy to maximise performance than to accelerate from Vx.
* Whilst the aircraft will be lower in the very early part of the climb (due to loss of climb performance due to acceleration) most of that energy would be able to be converted to height anyway.
Granted prior to an engine failure climbing at Vx will increase the chances of outclimbing the trees in front.
Logic suggests to me the Vy will give better obstacle clearance over trees following an engine failure for a number of reasons.
* The aircraft will be higher - meaning it will glide further and longer - creating a larger landing footprint.
* The aircraft will have traveled further - meaning the available landing footprint will be further in front of the aircraft.
* If it is only a partial engine failure Vx and Vy will become closer together - it is far easier to decelerate from Vy to maximise performance than to accelerate from Vx.
* Whilst the aircraft will be lower in the very early part of the climb (due to loss of climb performance due to acceleration) most of that energy would be able to be converted to height anyway.
Granted prior to an engine failure climbing at Vx will increase the chances of outclimbing the trees in front.
One thing to add, though, is that if a return to the airport is decided after the engine failure, use of Vy will shallow the climb angle overall, giving less margin in the glide back to the runway. Using your term, the available landing footprint BEHIND the aircraft is reduced with Vy.
Still, for most light singles, I would use Vy for initial climb. The performance difference between Vx and Vy is not that significant in most cases, and overall fuel economy and engine cooling are enhanced at the higher airspeed.
