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power recovery autorotations and quickstop


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Hi fellow pilots,

 

 

Can someone give me advice about the last part of the autorotation. Had different instructors and mixing things up because they all see it different.

 

I have problems with the flare and the power recovery at the end of the flare. Had some instructors but some learn to crack to trottle at 300 ft to 2000 RPM and some not. Some learn to check collective before the flare and some not.

 

My problems are:

Yawing at the end of the flare.

RRPM is to high or to low during the flare.

Why is the RRPM to high or to low when I start or at the end the flare?

How can i solve the wrong RRPM during the flare? Lower of check collective?

My instructors lowers collective during the flare, why is he doing that and is that not dangerious?

 

Same i have with the Quickstop.Again yawing and not the right steep approach.

 

Alot of questions but i need some professional help. As a student pilot i wanne be aware of these things.

 

Thank you for you help and fly safe

 

Dave]

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Yawing at the end of the flare.

 

What direction are you yawing? Is the yaw before or after you begin the power recovery?

 

RRPM is to high or to low during the flare.

 

There are several reasons why the RRPM may be too high/low during the flare. To high could be from too little collective check, or a flare that was too aggressive. To low could be from too much collective check, or a flare that is not aggressive enough.

 

Why is the RRPM to high or to low when I start or at the end the flare?

 

Depends on the situation, see the answer above,

 

How can i solve the wrong RRPM during the flare? Lower of check collective?

 

Again, it depends on what the problem is.

 

My instructors lowers collective during the flare, why is he doing that and is that not dangerious?

 

He may be lowering the collective during the flare to prevent a loss of RRPM, but he may have another reason.

 

Same i have with the Quickstop.Again yawing and not the right steep approach.

 

Not the right steep approach? What is the wrong one? Too steep, too shallow?

 

The best thing you can do is ask your instructor what your doing wrong. I could list all the possible things you could do wrong, but I would be here all night and it wouldn't do you any good.

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It sounds like your yaw problems happen when you add power after the flare in the auto and quickstop. Either your not anticipating the torque as you add power or your not anticipating left yaw when power is reduced (if your in a robbie or schweizer). I know its hard to coordinate your feet with your left arm but it will happen, soon enough you'll get it.

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What direction are you yawing? Is the yaw before or after you begin the power recovery?

There are several reasons why the RRPM may be too high/low during the flare. To high could be from too little collective check, or a flare that was too aggressive. To low could be from too much collective check, or a flare that is not aggressive enough.

Depends on the situation, see the answer above,

Again, it depends on what the problem is.

He may be lowering the collective during the flare to prevent a loss of RRPM, but he may have another reason.

Not the right steep approach? What is the wrong one? Too steep, too shallow?

 

The best thing you can do is ask your instructor what your doing wrong. I could list all the possible things you could do wrong, but I would be here all night and it wouldn't do you any good.

Thank you for your reply,

 

yawing is to the right at the end of the flare.

 

with the beginning quickstop i let the helicopter go down to much and the helicopter will yaw to the left

 

thank you for your help

 

It sounds like your yaw problems happen when you add power after the flare in the auto and quickstop. Either your not anticipating the torque as you add power or your not anticipating left yaw when power is reduced (if your in a robbie or schweizer). I know its hard to coordinate your feet with your left arm but it will happen, soon enough you'll get it.

 

What i am doing wrong i think is when i apply power back i do not give gradually left pedal but at the end of the flare full pedal to compensate.

 

Thank you for your help

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lazy feet!! took me ages to not to forget that I had them even know I sometimes seize up Oh! for a 520

 

When Training and doing Quick stops, I used to flair then pull collective to early and you get the dreaded porpoise effect let the nose settle then pull collective and feed in pedal gently as you do, it is a slower manover than you think.

I found that down wind 180s into Q\Stops were for me a lot smother, either pulling the nose up in the turn or after the turn into wind and for some reason it was always a nicer outcome! perhaps it was a feeling that if it was not done correctly all that would be left was a smoking heap, or because you were allready using your feet in the turn?.

RRPM in a 300 ( don't know about 22 only flown one for 0.1hrs )are not to difficult if you have correct speed you will get the hang of flicking a glance at the tach and either adjusting speed\ attitude to bring them up or just a breath of collective to keep them in the green, listen as well to the noise of the rotor it will tell you which way they are going do a couple of 180 or 360 from a good hight and you will get the feel I am sure

BUT your instructor should be telling you what is going wrong

 

BENNY DAVE5

I only did 2\3 autos autos to recovery, then always to the ground, so throttle was not a requirement the instructor rolled the throttle on when his nerve broke! he was always saying higher when we did Q stops, the early tendency for me was to fly TO low!! his nerve went when I dragged the skids at 60 Kts focused me to!!! a pucker moment if ever, still you learn real quick with the advantage of adrenalin

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Sounds like a foot problem. I remember having the same issue when I learnt to fly.

 

For the time being try forgetting about autorotations. Concentrate on getting the quickstop right first. A quickstop is really the bottom part of an autorotation, so if you get that right, then hopefully it will go someways to helping out the yaw on the recovery part of the auto.

 

When doing the quickstop do it very gently, with a small flare and focus on keeping your heading straight. Do it up and down a taxiway/runway where you have a line to help you keep track of where you're going. Once you have it mastered doing it gently, then you can gradually increase the amount of flare, which will necesitate increased collective inputs and therefore more pedal work. Remember that there is nothing 'quick' about a quickstop. It should be called a slow and smooth stop.

 

As far as the recovery on the auto goes it is very important to have your eyes looking out of the aircraft right up the taxi way/runway. Don't look at the ground too close to the aircraft. It's a hard habit to break because the ground comes up very fast and the tendency is to get fixated on it. During the flare tell yourself to look up at the horizon.

 

Hope that helps you a bit and let us know how it goes.

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Sounds like a foot problem. I remember having the same issue when I learnt to fly.

 

For the time being try forgetting about autorotations. Concentrate on getting the quickstop right first. A quickstop is really the bottom part of an autorotation, so if you get that right, then hopefully it will go someways to helping out the yaw on the recovery part of the auto.

 

When doing the quickstop do it very gently, with a small flare and focus on keeping your heading straight. Do it up and down a taxiway/runway where you have a line to help you keep track of where you're going. Once you have it mastered doing it gently, then you can gradually increase the amount of flare, which will necesitate increased collective inputs and therefore more pedal work. Remember that there is nothing 'quick' about a quickstop. It should be called a slow and smooth stop.

 

As far as the recovery on the auto goes it is very important to have your eyes looking out of the aircraft right up the taxi way/runway. Don't look at the ground too close to the aircraft. It's a hard habit to break because the ground comes up very fast and the tendency is to get fixated on it. During the flare tell yourself to look up at the horizon.

 

Hope that helps you a bit and let us know how it goes.

 

Hi Vaqueroaero,

 

Thank you for your good explinatioin. I will give it a try and use more pedal and do it more slowly.

 

When you are doing autorotations, when do you pull the collective in the flare?

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Hi Vaqueroaero,

 

Thank you for your good explinatioin. I will give it a try and use more pedal and do it more slowly.

 

When you are doing autorotations, when do you pull the collective in the flare?

 

99% of the autos that I do are to the ground. I find it harder now to do a power recovery than a full down. When doing a power recovery I always try and terminate in a hover at an altitude that I would feel comfortable rolling off the throttle and doing a hovering auto.

 

It is hard to put a firm number on when to pull collective because there are so many variables. The pitch pull is different, for example, on a day where there is a 15 knot headwind than on a day where the wind is calm. A calm wind day requires a more aggressive flare to bleed off ground speed than would a 15 knot headwind. (I always say that if you're going to have an engine failure have it on a windy day!) It depends on rotor RPM and grossweight. Can I use ground run or do I need to zero it out?

 

To answer your question though if I have to put an number on it, it would be about 15-20 feet. Once the helicopter is level then I pull the amount of pitch necessary to avoid bending something! Sometimes not much, other times full collective travel.

Levelling the helicopter is important (although not all - the Bell 407 you touchdown heels first) and the only way of doing it is as I previously stated - have your eyes looking outside and down the runway.

 

Keep working on them and it'll come.

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This website has some great info. I recommend to everyone. Check out this link for info on autos.

 

http://copters.com/pilot/autorotation.html

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lazy feet!! took me ages to not to forget that I had them even know I sometimes seize up Oh! for a 520

 

When Training and doing Quick stops, I used to flair then pull collective to early and you get the dreaded porpoise effect let the nose settle then pull collective and feed in pedal gently as you do, it is a slower manover than you think.

I found that down wind 180s into Q\Stops were for me a lot smother, either pulling the nose up in the turn or after the turn into wind and for some reason it was always a nicer outcome! perhaps it was a feeling that if it was not done correctly all that would be left was a smoking heap, or because you were allready using your feet in the turn?.

RRPM in a 300 ( don't know about 22 only flown one for 0.1hrs )are not to difficult if you have correct speed you will get the hang of flicking a glance at the tach and either adjusting speed\ attitude to bring them up or just a breath of collective to keep them in the green, listen as well to the noise of the rotor it will tell you which way they are going do a couple of 180 or 360 from a good hight and you will get the feel I am sure

BUT your instructor should be telling you what is going wrong

 

more and more the picture is coming together. When you check collective , do you gentle roll on trottle or full trottle.

 

thank you for you advice

 

This website has some great info. I recommend to everyone. Check out this link for info on autos.

 

http://copters.com/pilot/autorotation.html

 

 

good website and very detailled,

 

thank you

 

99% of the autos that I do are to the ground. I find it harder now to do a power recovery than a full down. When doing a power recovery I always try and terminate in a hover at an altitude that I would feel comfortable rolling off the throttle and doing a hovering auto.

 

It is hard to put a firm number on when to pull collective because there are so many variables. The pitch pull is different, for example, on a day where there is a 15 knot headwind than on a day where the wind is calm. A calm wind day requires a more aggressive flare to bleed off ground speed than would a 15 knot headwind. (I always say that if you're going to have an engine failure have it on a windy day!) It depends on rotor RPM and grossweight. Can I use ground run or do I need to zero it out?

 

To answer your question though if I have to put an number on it, it would be about 15-20 feet. Once the helicopter is level then I pull the amount of pitch necessary to avoid bending something! Sometimes not much, other times full collective travel.

Levelling the helicopter is important (although not all - the Bell 407 you touchdown heels first) and the only way of doing it is as I previously stated - have your eyes looking outside and down the runway.

 

Keep working on them and it'll come.

 

it is a long road but thing are getting more sense now.

 

thank you again for your advice

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I used to have slight issues with terminations during power recovery until an instructor said one small phrase with an emphasis I couldn't recall before. He said, "...slow and progressive deceleration." In the years since, it has made all the difference.

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Just found this article from 2004 in the R&W archives

FROM THE LEFT SEAT

 

Autorotation Training

 

Teaching autorotations requires training -- and remembering the basics

 

This accident happened with a high time CFI practicing auto-rotations to the taxiway with a CFI student. It was the usual hot summer day in sunny California--40 deg. Celsius with a density altitude of 3,800 ft., with high humidity. The instructor and his student were both heavy-set guys and unaware that they were close to maximum gross weight at takeoff. The wind was variable, ranging from 180 to 360 deg., and there were towering cumulus clouds in the surrounding mountains with a risk for thunderstorms. The active runway was designated 18, although the CFI was uncomfortable using taxiway 18 since the windsock shifted back and forth between north and south.

 

The instructor and his student practiced straight-in autos first, with the instructor noticing that he had to start his flare at approximately 60 ft. in order to level out in time.

 

According to the instructor, they had practiced at least 10 autorotations, with everything to an acceptable standard. At times the student had a tendency to lower the nose of the helicopter on entry and as a consequence kept too high forward airspeed in the glide. The rpm cautionary light and warning horn came on and the student was told to move the cyclic slightly aft to correct for the low rpm and high airspeed. When the student moved the cyclic aft too quickly, the rpm increased above the red line so the instructor took over the controls to prevent an overspeed on the rotor. He lifted the collective to bring down the high rpm and slowed the helicopter to 65 kt. airspeed with a gentle aft cyclic movement.

 

The instructor explained to the student that if he concentrated on keeping the nose level from the beginning to the end he would do much better. The student was instructed to look out at the horizon and bring the cyclic aft to level the ship in the entry, then lift the collective slowly to avoid a rise of rpm above the green. Before the entry, the relative wind comes from above the helicopter and moves downward through the rotor disc. But after the entry, the relative wind comes from below and moves into the rotor system, increasing blade speed. As a consequence, the collective may need to be raised a little bit in order to avoid an overspeed that can damage the spindle or put too much stress on the blades.

 

The instructor explained that for the two next stages, the flare and the power recovery, the perfect rpm was in top of the green in the glide with the airspeed set at 65 kt., with the aircraft in trim.

 

The straight-in autorotations were followed by 180 deg. autorotations. The entry was to be exactly the same as for the straight-in, but as the student turns the helicopter he can expect an rpm increase and may need to pull up on the collective, keeping the aircraft in trim during the turn toward the taxiway, maintaining a 65-kt. airspeed and getting rpm to the top of the green. If the collective is raised slightly, it must be lowered as the aircraft comes out of the turn. If not lowered, the flare portion will have a too low blade speed and airspeed, with an accident right around the corner.

 

After approximately 1.2 hours had been spent on autorotation practice, the student was told to finish the training with one more 180 deg. auto and that would be it for the day.

 

They took off and climbed to 700 ft. AGL on downwind. They had 75-kt. airspeed with the helicopter in trim. Everything looked normal. In the entry the student dipped the nose, rpm dropped and airspeed was approximately 75 kt. by the time the student became aware of the situation. He then moved the cyclic aft too rapidly and the rpm increased abruptly, passing the red-line. The instructor shouted to increase collective and push the cyclic forward to get the rpm back in top of the green and the airspeed back to 65 kt. But at that point everything was out of control. What the instructor and student did not know was that the wind had shifted from south to north and they had a 15 mph tailwind. They were descended rapidly, with too low an airspeed of approximately 45 kt. and with way too low rpm.

 

The instructor took the controls and flared, but did not have sufficient lift to stop the rate of descent. The aircraft contacted the taxiway hard, knocking off the tail boom. Miraculously both pilots survived, shaken but essential unharmed.

 

Analysis: This accident could have been avoided. The instructor knew about the high-density altitude condition, with limited lift due to the high-density altitude and high temperature. Aircraft performance decreases with higher than normal outside air temperatures and higher than normal density altitude conditions.

 

The instructor knew that he had not trained the student from the beginning. He did not really know the student's proficiency, since this was in the beginning of their training. He did not even talk to the student's former school for an opinion on the student's overall flying skills, attitude and judgment. The instructor also knew about the shifting wind conditions. The instructor should have monitored the windsock on downwind before entering the 180-deg. autorotation.

 

The CFI also should have done a weight and balance to determine whether or not they were below maximum gross weight. He never did this simple computation. Neither of them called the Flight Service Station to get a standard weather briefing. The Federal Aviation Regulations state that before take-off, a pilot needs to know " all aspects of that flight." That means visibility, ceiling, wind direction, wind speed, temperature, density altitude, dew point, pilot reports, Notams, TFRs and any other information relative to the flight.

 

The instructor also made the lesson too long. One hour lessons are less tiring than dragging it to overtime.

 

The rate of descent in an autorotation under normal conditions is approximately 1500 ft. per minute in the glide. In this accident the instructor stated that their rate of descent was approximately 1800 ft. per minute or more.

 

Rpm can be controlled either by the collective or the cyclic. Unlike in normal flight, if a higher than normal rpm occurs, it can be brought down by slightly raising the collective, thus increasing the angle of attack on both blades, or by moving the cyclic forward. If we have a lower than usual rpm setting, we can bring the rpm back into the green arc by lowering the collective, decreasing the angle of attack on both blades, or by moving the cyclic aft.

 

Sometimes the rpm fluctuations are large and quick action of both collective and cyclic is required to control the rpm.

 

It is also of great importance to keep a safe airspeed in the glide. Airspeed is controlled by a combination of cyclic, collective and pedals. The aircraft must be flown in a trimmed condition to decrease excessive drag, otherwise the glide distance is shortened and the chosen spot may be missed.

 

Maximum glide distance is achieved by a lower rpm, higher airspeed and in trim. After the entry the collective must be pulled up to establish a low rpm setting and the cyclic moved forward to get the higher airspeed to extend the glide.

 

To be an autorotation specialist, you should go out and practice each step of the autorotation separately. Begin the practice with the entry stage. Make sure that each and every autorotation starts from at least 500 ft AGL, with minimum airspeed of 70 kt. headed into the wind.

 

Lower the collective full down until the Sprague clutch disengages the engine from the rotor blades. If you enter the autorotation gently and smoothly you won't even know you are in an autorotation glide.

 

It is amazing what a difference a smooth entry can do for you. When you enter the auto, make sure you hold the cyclic aft, with level attitude, looking out at the horizon. The slightest nose down will destroy the "good feeling" of entering a perfect auto. You should have a feeling of sailing when you lowered the collective correctly.

 

If the aircraft is allowed to nose over, do a recovery and practice until you are able to do the entry perfectly. The entry is the " secret" of the autorotation. If you nose the helicopter up, you will end up with rpm too high and airspeed too slow. Try again! Once you can do them perfectly over and over again you have it made!

 

To practice the glide, climb to 5,000 ft. and enter autorotation, showing the student how to control the rpm with both the collective and cyclic. Practice the first 5,000-ft. autorotation controlling rpm with collective only, then practice a second 5,000-ft. auto controlled by cyclic only.

 

Finally, practice using both collective and cyclic. Slow down the airspeed, then increase it. Practice 360 deg. turns, watching the rpm gage to see how the rpm increases in the turn and decreases after the turn is made.

 

The third stage in the autorotation is the flare. At 40 ft. and 65 kt. airspeed, with the rpm in the lower green arc, start the flare by looking out at the horizon, keeping the heading straight.

 

The flare must be done nice and gentle during practice. If you flare too hard or abrupt, the rotor disc will get you into a climb instead of getting you closer to the ground--not the intent of the flare. Start out slow and progressively increase the flair until the aircraft has descended to about 8 ft., then level the ship and perform a running landing on asphalt or any other firm, smooth terrain, or do a hovering auto on rough terrain.

 

Under ideal conditions, and to practice to reach optimum proficiency, practice to a full-stop hovering autorotation. At the beginning of the flair, move the cyclic aft, gradually increasing the tip path plane until the rate of descent and forward airspeed have decreased to a full stop at a 5-ft. hover with collective remaining. From that altitude it is easy to do a hovering autorotation.

 

Make sure you are looking out on the horizon to keep the aircraft straight. If not, you might roll the aircraft if you perform full touch down practice landings. Practice the flare with cyclic only and with collective and cyclic together.

 

Practice the full touch down auto and hovering auto technique with an experienced instructor so you know both techniques. And make sure you don't overspeed the rpm when you do the flare portion. If you move the cyclic aft too fast you will end up with too high rpm, and the only way to get it down is to lift the collective.

 

The last portion of the autorotation is the power recovery. After you have leveled the ship at 8 ft., start to lift the collective smoothly, apply left pedal and increase the rpm back into the green arc gently, but firmly.

 

If the helicopter drifts right, apply left cyclic to keep a straight ground track. If the warning horn and light comes on you must increase rpm rather quickly and milk the collective, lowering it gently while rolling on the rpm.

 

Then, and only then, lift collective to avoid a hard landing. Many hard landing training accidents have occurred after leveling out and doing a wrong power recovery. Increasing the rpm itself is almost impossible, you must milk the collective to get the rpm back in top of green. On hot summer start the first autorotation at 50-60 ft. to give yourself room to complete the flare without coming too close to the ground. After that first high auto you can do them closer to the ground. The variables will determine how close you can go. But there is no reason to go below 40 ft. unless you are practicing full touch down autos.

 

Different helicopters have different entry altitudes, glide speeds and flare altitudes. Make sure you read the pilot's operating handbook for each and every helicopter type you are going to fly. Get good instruction from a professional CFI and 10 hours of autorotation practice is good training investment.

 

Make sure you attend the helicopter factory safety course each and every year, because that is well worth money. Because what if...?

 

Johan Nurmi is an FAA Gold Seal Instructor pilot with the USA Academy of Aviation, French Valley Airport, Murrieta, Calif.

--Source

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