Autorotative recovery from different flight regimes
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Autorotative recovery from different flight regimes
I would be very grateful to anyone who could offer some answers to the following -
Two scenarios, the first is flight over irregular terrain such as this first photo.
Scenario 1
This is an Astar American Squirrel flying in Hawaii
In the above photo the Astar is operating a scenic tourist flight. The tourists enjoy the dramatic landscape and scenery, which I understand. My question is - if the engine cut at the time of this photo what is the pilot trained to do?
My next question is - who determines the safe flight routes for tourist flights and is this same rugged terrain the same for the Grand Canyon?
Scenario 2
The Bell 206 spraying
If you are flying maybe at 80, 90 or even 100 knots and you are very low level, such a when spraying, and the engine cuts, what does the pilot do? Is there anything he can do?
Who makes the risk assessment for agricultural flying?
Thanks in advance.
Just trying to understand how pilots get out of tricky situations and how they get into them in the first place.
Two scenarios, the first is flight over irregular terrain such as this first photo.
Scenario 1
This is an Astar American Squirrel flying in Hawaii
In the above photo the Astar is operating a scenic tourist flight. The tourists enjoy the dramatic landscape and scenery, which I understand. My question is - if the engine cut at the time of this photo what is the pilot trained to do?
My next question is - who determines the safe flight routes for tourist flights and is this same rugged terrain the same for the Grand Canyon?
Scenario 2
The Bell 206 spraying
If you are flying maybe at 80, 90 or even 100 knots and you are very low level, such a when spraying, and the engine cuts, what does the pilot do? Is there anything he can do?
Who makes the risk assessment for agricultural flying?
Thanks in advance.
Just trying to understand how pilots get out of tricky situations and how they get into them in the first place.
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Your risk assessment of Ag ops will tell you that there is more chance of a wire strike or colliding with the ground/tree etc than there is of an engine failure.
But you can auto from very low altitudes successfully, I know people that have done it.
But you can auto from very low altitudes successfully, I know people that have done it.
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HS: It is energy, not height, that is important for autorotation entry. That energy may be height, speed, or Nr/inertia. Height adds glide distance as well. Nr/inertia can add time.
This info and more is in the various books available on helicopter aerodynamics and basics of flying.
This info and more is in the various books available on helicopter aerodynamics and basics of flying.
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Disclaimer: This is not permission to try this! These remarks are addressed to professional pilots!
In my experience, a lot depends on the machine. The 206 family is probably the best machine for low-level autos, in terms of high inertia blades and crashability - not all machines have both!
When I did power line survey, we taught the guys just to take what was below - if they were very slow and low, a slight check back on the cyclic, DUMP THE COLLECTIVE and haul it in very quickly at the bottom (there's a great article about this by Dennis Venturi (no relation, I'm sure) in Helicopters Magazine some years ago (in Canada). Briefly he points out that if you do a quick pullup on an aerofoil you will generate a vortex across the top surface keeps the boundary layer to it and you will be able to go beyond the static stall for a second or two - possibly generating double the lift. Look for dynamic stall at NASA AMES as well for more info. The jettie will do a vertical from 50-75 feet BUT - as Shawn Coyle pointed out in another post some time ago - that was a test situation - in a real engine failure at that height (and arguably at any lowish height) you would likely be on the ground before you realised what was going on if you are not paying attention.
I would always try to do a vertical, even at the top of the H/V curve, which is 400 feet in the 206. But that's my personal choice, knowing the machine as I do.
If you had some speed on, cyclic right back, zoom climb and see what's below - the Gazelle does this admirably. Again, it depends on the machine.
The operator should be determining the safe routes in the first instance. In a valley as in Scenario 1? You would have to perform a controlled crash - also look for a US Army document called how to crash a helicopter.
Tin helmet is now on....
Phil
In my experience, a lot depends on the machine. The 206 family is probably the best machine for low-level autos, in terms of high inertia blades and crashability - not all machines have both!
When I did power line survey, we taught the guys just to take what was below - if they were very slow and low, a slight check back on the cyclic, DUMP THE COLLECTIVE and haul it in very quickly at the bottom (there's a great article about this by Dennis Venturi (no relation, I'm sure) in Helicopters Magazine some years ago (in Canada). Briefly he points out that if you do a quick pullup on an aerofoil you will generate a vortex across the top surface keeps the boundary layer to it and you will be able to go beyond the static stall for a second or two - possibly generating double the lift. Look for dynamic stall at NASA AMES as well for more info. The jettie will do a vertical from 50-75 feet BUT - as Shawn Coyle pointed out in another post some time ago - that was a test situation - in a real engine failure at that height (and arguably at any lowish height) you would likely be on the ground before you realised what was going on if you are not paying attention.
I would always try to do a vertical, even at the top of the H/V curve, which is 400 feet in the 206. But that's my personal choice, knowing the machine as I do.
If you had some speed on, cyclic right back, zoom climb and see what's below - the Gazelle does this admirably. Again, it depends on the machine.
The operator should be determining the safe routes in the first instance. In a valley as in Scenario 1? You would have to perform a controlled crash - also look for a US Army document called how to crash a helicopter.
Tin helmet is now on....
Phil
Last edited by paco; 28th Aug 2013 at 12:31.
My question is - if the engine cut at the time of this photo what is the pilot trained to do?
It can be very deceptive when you only have a photographic view vs being there in person and knowing the approved landing spots.
The FAA in conjunction with the operators determined the "scenic areas" and various transition segments and routes. An operator had to be signatory to the "letter of agreement" and be issued "Ops Specs" in order to utilize them or else had to remain above 1,500 AGL except for take off and Landing. Of course these days we have FAR 136 which you can read all about Here.
Heli,
Spraying is not done at the high speeds you mentioned.
Generally speaking.....when spraying you are going to take what is just in front of you...and try to use what airspeed you have to add to your Rotor Inertia.
In the Sight Seeing photo.....or when over terrain that does not provide nice landing spots....seek the lowest, softest, smoothest, least wet place you can.
Fluffy short green Trees are softer than tall, dark ones.
Remember in forested areas...areas of new growth probably have old Stumps hidden by the new Trees. Aim for a trail or track where you can see there are no stumps.
Personally, I opt to keep my airspeed up, pick the best looking area in general, and when you get right down to the Decision Point....pick what looks the best....and try to arrive at the tree tops with as much Nr as you can and as little forward airspeed as you can....and use up all that Nr slowing your ROD to the minimum possible as you enter the Trees staying as level as possible or very slightly nose high.
Unless there is a "good" place that you can easily make....don't try for one and land short out of Nr. We live and die by Nr....or the lack of it.
Spraying is not done at the high speeds you mentioned.
Generally speaking.....when spraying you are going to take what is just in front of you...and try to use what airspeed you have to add to your Rotor Inertia.
In the Sight Seeing photo.....or when over terrain that does not provide nice landing spots....seek the lowest, softest, smoothest, least wet place you can.
Fluffy short green Trees are softer than tall, dark ones.
Remember in forested areas...areas of new growth probably have old Stumps hidden by the new Trees. Aim for a trail or track where you can see there are no stumps.
Personally, I opt to keep my airspeed up, pick the best looking area in general, and when you get right down to the Decision Point....pick what looks the best....and try to arrive at the tree tops with as much Nr as you can and as little forward airspeed as you can....and use up all that Nr slowing your ROD to the minimum possible as you enter the Trees staying as level as possible or very slightly nose high.
Unless there is a "good" place that you can easily make....don't try for one and land short out of Nr. We live and die by Nr....or the lack of it.
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Thanks for the insight. 
Gordy, sounds like they've got it well organised in Hawaii then.
Paco, if when spraying and the engine quits the pilot goes into a climb first which I understand would be required to gain some height, would this be done with the collective lever up or would it need to go down straight away like for a normal autorotation?
Gordy, sounds like they've got it well organised in Hawaii then.
Paco, if when spraying and the engine quits the pilot goes into a climb first which I understand would be required to gain some height, would this be done with the collective lever up or would it need to go down straight away like for a normal autorotation?
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If it's a good field and you're in the right position, just land ahead, but I did forests over in Nova Scotia, and you would have tumbled over at any speed (as SASless says, you don't spray at high speed) - part of the reason for the "climb" is to get the speed back as well so you can drop in between the stumps.....
But yes, at the same time as pulling back the cyclic you would lower the collective.
Phil
But yes, at the same time as pulling back the cyclic you would lower the collective.
Phil
My preferred method on doing a cyclic climb is to hold the collective "up" until the airspeed drops and the Nr has climbed....then lower to the collective to maintain Nr. That allows for a greater gain in height as compared to lowering the collective and then doing the cyclic climb. Of course.....lots of variables in the situation and those will drive what actions one takes.
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Next time you go flying.....try doing your standard text book "Quick Stop"....and then try the frozen collective....cyclic climb and you will see the difference in the results. The objectives of the two maneuvers are quite different so study up on them and make sure you understand what the differences are and what you should be looking for while doing them.
Do keep your tail rotor out of the dirt!
Do keep your tail rotor out of the dirt!
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Ok Sir!
In summary then - when flying over rugged terrain such as Hawaii try and get as much height as you can and fly over areas where there are potential landing spots in case of an engine failure and when spraying, if the engine cuts, initially keep some collective applied, climb to gain height and then perform a cushioned landing as you would if you were doing an auto from within the HV cure such as might be necessary if you had an engine failure while using a long sling line?
In summary then - when flying over rugged terrain such as Hawaii try and get as much height as you can and fly over areas where there are potential landing spots in case of an engine failure and when spraying, if the engine cuts, initially keep some collective applied, climb to gain height and then perform a cushioned landing as you would if you were doing an auto from within the HV cure such as might be necessary if you had an engine failure while using a long sling line?
Don't mix Longline flying into this....as that opens up a whole new can of worms.
In a single engine helicopter....when it comes to engine failures....Altitude is your friend. Planning your route to favor suitable landing sites is a good plan as well.
Spend some time with your Instructor(s) discussing all this.
In a single engine helicopter....when it comes to engine failures....Altitude is your friend. Planning your route to favor suitable landing sites is a good plan as well.
Spend some time with your Instructor(s) discussing all this.
As has been mentioned above, it's energy that counts.
Low and fast, you can briefly freeze the collective and cyclic climb until the tail is far enough from the ground/obstacles to then allow you to dump the collective whilst flaring pretty hard to rebuild rotor rpm.
When you are slow enough, or you start to sink in the flare and don't have enough left to keep the tail off the ground, level it and cushion on.
For a low level auto you can either do this 'zoom' method, which trades speed for height and therefore reduces your distance before reaching the ground, or do a progressive long flare which will take you further over the ground. Either way it's a tradeoff between lowering the collective (preserving rpm but dropping you towards the ground) and cyclic flare (building rpm and holding you up, at least until you run out of speed).
The key for me is get rid of the forward speed, unless there's a nice flat football field dead ahead.
Low and fast, you can briefly freeze the collective and cyclic climb until the tail is far enough from the ground/obstacles to then allow you to dump the collective whilst flaring pretty hard to rebuild rotor rpm.
When you are slow enough, or you start to sink in the flare and don't have enough left to keep the tail off the ground, level it and cushion on.
For a low level auto you can either do this 'zoom' method, which trades speed for height and therefore reduces your distance before reaching the ground, or do a progressive long flare which will take you further over the ground. Either way it's a tradeoff between lowering the collective (preserving rpm but dropping you towards the ground) and cyclic flare (building rpm and holding you up, at least until you run out of speed).
The key for me is get rid of the forward speed, unless there's a nice flat football field dead ahead.
The German Army used to advocate leading with collective at very low level to get the tail away from the ground before flaring off the speed and recovering the Nr.
Aye Crab....but they flew VERY low to the ground didn't they....something a Civvie Pilot would be a very naughty boy for doing.
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In the video below the pilot gives a running commentary and states at 02:05 that he is flying about 3ft above the crop, what would German army pilots be doing flying that low?
Arm out the window, what you have said is more or less what I've been told Ag pilots learn to do.
Heli Lad,
You are not spraying crops.
When you get to that level of flying as a commercial pilot earning your keep flying helicopters....then you might have need of these kinds of techniques.
Until then....stick to what your Instructors are teaching you while you study up on other techniques and procedures. Discuss it all with them and incorporate some of all this into your training flights to broaden your experience level but do so as part of your flying with your Instructors.
Just as I advised not getting into discussions about Long Lining....Spray flying is an altogether kettle of fish as well.
I am sure Crab will pass himself as an expert on Spraying but and German Army Flight Techiques but he does have a privileged point of view being our Resident SAR expert.
You are not spraying crops.
When you get to that level of flying as a commercial pilot earning your keep flying helicopters....then you might have need of these kinds of techniques.
Until then....stick to what your Instructors are teaching you while you study up on other techniques and procedures. Discuss it all with them and incorporate some of all this into your training flights to broaden your experience level but do so as part of your flying with your Instructors.
Just as I advised not getting into discussions about Long Lining....Spray flying is an altogether kettle of fish as well.
I am sure Crab will pass himself as an expert on Spraying but and German Army Flight Techiques but he does have a privileged point of view being our Resident SAR expert.
