Downwind Autorotations?
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From downwind, 50 feet and 130 knots its going to take a very talented and wide awake driver to turn into wind from an unexpected engine failure. From experience I know that it takes a second or two to even have the brain admit that the engine has failed, despite the evidence in front of you, and only then will the reflexes take over. I would not even try to turn around, at 50 feet and 130 buttons you will not make it to an open spot you just flew over even if you are expecting it. It all sounds good in theory, reality bites.
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I only had 1 engine failure in a Gazelle. Luckily it was into wind. (and conveniently at a 5 ft hover!)
In the scenario you proposition above, I'd recommend that following the zoom to 300 feet [or whatever is achievable] you ensure you have 20 knots plus the wind speed indicated and do not turn more than 100 degrees until you have positively identified and selected the point to go to. The turn should be a low angle [less than 15 degrees of bank] without attitude correction. Once into wind you can then adjust accordingly and as you mention, minimum TD velocity in both directions is preferable.
I only had 1 engine failure in a Gazelle. Luckily it was into wind. (and conveniently at a 5 ft hover!)
In the scenario you proposition above, I'd recommend that following the zoom to 300 feet [or whatever is achievable] you ensure you have 20 knots plus the wind speed indicated and do not turn more than 100 degrees until you have positively identified and selected the point to go to. The turn should be a low angle [less than 15 degrees of bank] without attitude correction. Once into wind you can then adjust accordingly and as you mention, minimum TD velocity in both directions is preferable.
Avoid imitations
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One great big reason for not landing downwind unless there's no other option is "the gatepost".
Downwind 10 kts is 20 kts ground speed worse than 10 kts into wind.
Assuming, despite the odds, that you manage, somehow, to make a smooth but downwind run-on landing in Farmer Giles' field. Then you have to contend with "the gatepost".
You first see the gatepost some tens of yards away, just as you lose directional control of the aircraft on the wet grass. The gatepost comes rapidly towards the aircraft and you suddenly realise you are going to have to stop it between your legs....
Turning 90 degrees to a crosswind position is better than stuffing up Nr by trying to turn a full 180 degrees.
Downwind 10 kts is 20 kts ground speed worse than 10 kts into wind.
Assuming, despite the odds, that you manage, somehow, to make a smooth but downwind run-on landing in Farmer Giles' field. Then you have to contend with "the gatepost".
You first see the gatepost some tens of yards away, just as you lose directional control of the aircraft on the wet grass. The gatepost comes rapidly towards the aircraft and you suddenly realise you are going to have to stop it between your legs....
Turning 90 degrees to a crosswind position is better than stuffing up Nr by trying to turn a full 180 degrees.
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Originally Posted by A.Agincourt
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I am not too sure to what you are referring. If you could post a reference or something.
Originally Posted by chuteless
: A.Agincourt must own a huge amount of teddies
when he throws one away it seems to get replaced awful quick
when he throws one away it seems to get replaced awful quick
New pram on order?
Back OT, not only Mil spend lots of time below 500ft. A lot of my ops are in the 50 - 250' area, filming, sling loads, etc. I make sure that my refresher training includes low level autos, with 50ft/60kts as a normal entry.
The concept of continuing on for a downwind touchdown is one that I've not considered before this discussion: I'll certainly give it some thought, but I'm not sure that I'd be happy to risk an aircraft on a training sortie
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I don't want to completely hijack this thread, but I have a question that is somewhat related:
I am an EMS helicopter based at an airport. Depending on the wind speed & direction, for departure I will either hover over to a nearby parallel taxiway for take-off, or simply pedal turn into wind and perform a max performance take-off from my helipad, directly over the power lines. Unless the wind is a very stiff crosswind or tailwind, I always prefer to use the taxiway for departure, willing to accept that I am not into wind in exchange for a more suitable area to perform an emergency landing, if need be...
My question is: Assuming the wind is about ~12 knots or less, would you prefer to accept a crosswind, tailwind/quartering tailwind in order to be able to utilize the paved taxiway for departure, or would you rather take off into wind, going right through the shaded portion of the H/V diagram?
I am an EMS helicopter based at an airport. Depending on the wind speed & direction, for departure I will either hover over to a nearby parallel taxiway for take-off, or simply pedal turn into wind and perform a max performance take-off from my helipad, directly over the power lines. Unless the wind is a very stiff crosswind or tailwind, I always prefer to use the taxiway for departure, willing to accept that I am not into wind in exchange for a more suitable area to perform an emergency landing, if need be...
My question is: Assuming the wind is about ~12 knots or less, would you prefer to accept a crosswind, tailwind/quartering tailwind in order to be able to utilize the paved taxiway for departure, or would you rather take off into wind, going right through the shaded portion of the H/V diagram?
The Original Whirly
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Turning 90 degrees to a crosswind position is better than stuffing up Nr by trying to turn a full 180 degrees.
But turning through 180 degrees could be near to impossible at times. Is there anything against a crosswind auto other than the fact you now have nil wind conditions?
Avoid imitations
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As long as you can deal with the lateral drift, no.
Is there anything against a crosswind auto other than the fact you now have nil wind conditions?
Whirly - depending on which side the wind is coming from and which way your rotor turns it could have a serious impact on directional control, especially as Nr decreases during the cushion and the TR loses effectiveness.
The Gazelle (clockwise rotation when viewed from above) would run out of left pedal during the run on with any significant crosswind from the right. Because you are slowing the rotor down during the application of collective, the torque reaction works in the opposite way to normal and tries to yaw the fuselage right (in the case of the Gazelle) - this effect is exacerbated by the weathercock effect of the crosswind which is also trying to yaw the fuselage right into wind.
In my experience, the zoom climb from low level, 180 EoLs in the Gazelle were only ever achieveable as a pre-briefed exercise and in the real case would be very unlikely to work given a normal delay for recognition of the failure and the subsequent reaction.
The Gazelle (clockwise rotation when viewed from above) would run out of left pedal during the run on with any significant crosswind from the right. Because you are slowing the rotor down during the application of collective, the torque reaction works in the opposite way to normal and tries to yaw the fuselage right (in the case of the Gazelle) - this effect is exacerbated by the weathercock effect of the crosswind which is also trying to yaw the fuselage right into wind.
In my experience, the zoom climb from low level, 180 EoLs in the Gazelle were only ever achieveable as a pre-briefed exercise and in the real case would be very unlikely to work given a normal delay for recognition of the failure and the subsequent reaction.
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helicfii:
In any event, the answer in my book is that you select that which you are the most comfortable with at that time. Some might take the view that the percentage chance of you needing the 'nicer' area for EOL is so much less than the requirement for 'alternatives' ..........always your call.
In some cases, for most of the time, there is often a greater danger from mishandling the aircraft due to adverse weight, wind, obstacles or other and or a combination. Clearly, for the most part, the chances of having everything just so are so small you can count on one hand. [If EMS can count that is] The secret for any pilot is to determine the plan of action that has the least potential unwanted consequence.
To my mind the best solution is usually the one where the following are true:
The value of power/pitch/Tq is the absolute minimum you can achieve, below translational lift speed, the fuselage is pointing into wind. But it all depends upon specific aircraft type characteristics.
Best Wishes
Depending on the wind speed & direction, for departure I will either hover over to a nearby parallel taxiway for take-off, or simply pedal turn into wind and perform a max performance take-off from my helipad, directly over the power lines. Unless the wind is a very stiff crosswind or tailwind, I always prefer to use the taxiway for departure, willing to accept that I am not into wind in exchange for a more suitable area to perform an emergency landing, if need be...
In some cases, for most of the time, there is often a greater danger from mishandling the aircraft due to adverse weight, wind, obstacles or other and or a combination. Clearly, for the most part, the chances of having everything just so are so small you can count on one hand. [If EMS can count that is] The secret for any pilot is to determine the plan of action that has the least potential unwanted consequence.
My question is: Assuming the wind is about ~12 knots or less, would you prefer to accept a crosswind, tailwind/quartering tailwind in order to be able to utilize the paved taxiway for departure, or would you rather take off into wind, going right through the shaded portion of the H/V diagram?
The value of power/pitch/Tq is the absolute minimum you can achieve, below translational lift speed, the fuselage is pointing into wind. But it all depends upon specific aircraft type characteristics.
Best Wishes
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Whirlybird
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Turning 90 degrees to a crosswind position is better than stuffing up Nr by trying to turn a full 180 degrees.
I wondered about that. Particularly in an R22, don't think I'd fancy a downwind auto at all!!! But turning through 180 degrees could be near to impossible at times.
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Turning 90 degrees to a crosswind position is better than stuffing up Nr by trying to turn a full 180 degrees.
I wondered about that. Particularly in an R22, don't think I'd fancy a downwind auto at all!!!
But turning through 180 degrees could be near to impossible at times.
Is there anything against a crosswind auto other than the fact you now have nil wind conditions?
If you are really too close, and dependant upon height of entry, you can go past 90 degrees and allow the wind to blow you down wind of the TD point. However, I'd never do a manouvre like this unless I had a comfortable speed and that value is pretty much dependant upon type and the strength of the wind from the surface up to about 500 feet ish.
Auto's cross wind are not a problem so long as you plan to land into wind at the bottom. Otherwise, you could be in trouble.
Best Wishes
Last edited by A.Agincourt; 23rd Apr 2008 at 10:18. Reason: Just fishing
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chuteless
not quite a teddy but the best I could do at short notice
(don't try this downwind your glide ratio will be reduced
)
http://www.freegamesonline.dk/funnyg...nnon/index.php
not quite a teddy but the best I could do at short notice
(don't try this downwind your glide ratio will be reduced
)http://www.freegamesonline.dk/funnyg...nnon/index.php
Thank you dear chap, excellent fun and appealed to my sense of humour. 1815 I got.
Best wishes
Last edited by A.Agincourt; 23rd Apr 2008 at 13:11. Reason: Score Update
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Originally Posted by A.Agincourt
"as a junior sub on 826". My pram has a current MOT and offers verrrry verrry good MPG. Does that answer your question old boy?
A.A - just exactly how do high angles of bank and 'dizzying turns' reduce the RRPM then?
The original question was not about how you position for an EoL but whether or not the EoL itself could be carried out downwind.
Ahhh - nice try AA I see you have edited your post to remove the bull
The original question was not about how you position for an EoL but whether or not the EoL itself could be carried out downwind.
Ahhh - nice try AA I see you have edited your post to remove the bull
Last edited by [email protected]; 23rd Apr 2008 at 13:38. Reason: AAgincourt changing his post and hoping no-one would notice
Crab is 100% correct:
In reality we weren't often exactly 180' downwind when blatting about max chat at 50ft.
So the zoom climb auto, even if a bit delayed by reaction, would give you the slim chance of a. getting the speed off and b. turning 40 or 50 degrees and landing into wind.
If possible choice of fast low level transit in Germany was over trees, at tree top height, about 100-200m inside the tree line. (There were a lot of forests in our area of interest. ) A zoom auto (in theory) would get you to the surrounding countryside!
In my experience, the zoom climb from low level, 180 EoLs in the Gazelle were only ever achieveable as a pre-briefed exercise and in the real case would be very unlikely to work given a normal delay for recognition of the failure and the subsequent reaction.
So the zoom climb auto, even if a bit delayed by reaction, would give you the slim chance of a. getting the speed off and b. turning 40 or 50 degrees and landing into wind.
If possible choice of fast low level transit in Germany was over trees, at tree top height, about 100-200m inside the tree line. (There were a lot of forests in our area of interest. ) A zoom auto (in theory) would get you to the surrounding countryside!
I found throttle initiated LL EOLs on the Gazelle bad enough in-to wind!!!
My solution was to cheat and fly the Chinook! What wind? and great single engine hover performance (even if downwind). Hats off to those that flew heavier Gazelles operationally where this must have been a genuine concern.
I've just had a mental thought of doing a 180 EOL at LL and it brought me out in a chill - still, like FW turnbacks, if all you've got is behind you then needs must. I agree with the Trimmers on this thread, if you're confident you can cope with a X-Wind run on then any turn towards wind will reduce the space you require..but I think, like FW, it's important to have a point above the ground where you go wings level and concentrate on the tricky bit. Too many people have got fixated on the turn and not made the landing...
My solution was to cheat and fly the Chinook! What wind? and great single engine hover performance (even if downwind). Hats off to those that flew heavier Gazelles operationally where this must have been a genuine concern.
I've just had a mental thought of doing a 180 EOL at LL and it brought me out in a chill - still, like FW turnbacks, if all you've got is behind you then needs must. I agree with the Trimmers on this thread, if you're confident you can cope with a X-Wind run on then any turn towards wind will reduce the space you require..but I think, like FW, it's important to have a point above the ground where you go wings level and concentrate on the tricky bit. Too many people have got fixated on the turn and not made the landing...
The Army Gazelles we were operating at the time were actually even lighter than the RAF training machines;
No stab. Not one piece of Nav equipment, (not even minitans) No observer sight. Often no observer!
Like the Chinook, the Gazelle had great single engine performance..even downwind!!!
No stab. Not one piece of Nav equipment, (not even minitans) No observer sight. Often no observer!
Like the Chinook, the Gazelle had great single engine performance..even downwind!!!