Flight in the nasty part of the H-V diagram

[PA Pilot]

Suppose you are flying at high speed and are low, and that there is an engine, transmission, TR, or whatever failure. I don't see any way you could get yourself into an autorotative state. But, assuming you were able to keep the ship straight and had enough rotor inertia, would a flare with lowered collective, pretty much like a quick stop, allow you to convert all that airspeed to rotor RPM, slow the ship, and then let you cushion the touchdown in the same way you would do it in an auto? Assuming you didn't run into anything, of course!

 

Mind you, I have no intention of trying this, but I'm curious if the aerodynamics would work...

[FlyNHighNFast]

If you are going fast enough, you could try and trade speed for altitude. But over 60 knots you would have to be pretty low for that to be a problem (assuming you are in a R-22)

[Pogue]

Suppose you are flying at high speed and are low, and that there is an engine, transmission, TR, or whatever failure. I don't see any way you could get yourself into an autorotative state. But, assuming you were able to keep the ship straight and had enough rotor inertia, would a flare with lowered collective, pretty much like a quick stop, allow you to convert all that airspeed to rotor RPM, slow the ship, and then let you cushion the touchdown in the same way you would do it in an auto? Assuming you didn't run into anything, of course!

Yep... as long as you interpret your problem and act prior to tying the low altitude record. That's why there's the secondary high speed area in the height velocity graph - to give you enough altitude (time) to enter a flare and recover your rotor rpm.

[Paisley]

I was practicing a qick stop one time with a student at about 40ft AGL and 40kts in a R-22 and instead of lowering collective / aft cyclic he rolled the throttle off. The rotor rpm droped rapidly with the decreasing engine rpm so I flared and managed to keep the rotor rpm up until I could lower the collective and roll throttle on to join the needles. There was just enough inertia in those little blades to pull it off and recover. You can lose inertia quickly in a small helicopter like that but you can also gain it back just a quick.

[spencer]

Autorotations are all about Energy manipulation. For example at low altitude and high airspeed with normal RPM you can adjust the three factors of energy to make it all work out. For example lets say we are in an R-44 flying at 1000 ft agl with 120 kts. If i chop the throttle and in stead of lowering the collective you pull back on the cyclic (doesn't need to be abrupt) you trade off all of that airspeed for altitude. If you do pull back abrupt the r-44 will climb a little in the auto but realize that as your airpeed slows and you begin to enter the normal autortation you will have to lower the collective at that point. It is no different doing this procedure at 10 ft agl i know because i have tried it. I make it a personal rule that i will not fly the aircraft in a certain point on the height velocity diagram unless i know i can perform an autortation from that point. So for example when i had to do flights fast and low over the water(boat races), i went out and practiced doing autoroations from this point so that i know i can do it and it made the flight that much safer.

 

Disclamer: Keep in mind the above statement was in regards to an r-44 not an r-22. Don't try this unless accompied by a CFI familar with the maneuver in a particular type of aircraft.

[John90290]

I think it might look like this....survivable I would presume but not a text book auto.

 

http://www.griffin-helicopters.co.uk/video...sp?videokey=462

 

NTSB Identification: DEN02LA013.

 

The helicopter was fueled to capacity the evening before, and the engine compartment was preheated before departure. Preflight inspection revealed no frost on the airframe or rotor blades. The particle separator was clean and dry. Engine start and takeoff were normal. After crossing a highway 1/2 mile south from the heliport, at an airspeed "in excess of 50 mph [and] at an altitude of approximately 50-70 feet," the engine "flamed out." There was a noticeable yaw and the pilot heard "the sound of the engine shutting off." He autorotated towards a highway right-of-way. The helicopter struck the ground hard and slid 20 to 30 feet. "Mast bumping" broke the rotor head off. It struck the rear of the helicopter, severing the tail section. The helicopter spun around and rolled over on its right side.

[lelebebbel]

Suppose you are flying at high speed and are low, and that there is an engine, transmission, TR, or whatever failure. I don't see any way you could get yourself into an autorotative state. But, assuming you were able to keep the ship straight and had enough rotor inertia, would a flare with lowered collective, pretty much like a quick stop, allow you to convert all that airspeed to rotor RPM, slow the ship, and then let you cushion the touchdown in the same way you would do it in an auto? Assuming you didn't run into anything, of course!

 

Mind you, I have no intention of trying this, but I'm curious if the aerodynamics would work...

 

you didn't say what helicopter you were talking about, but at least in the r22/44 the low+fast section of the HV diagram starts at 50-60 knots and the shaded area goes up to 25agl.

 

Here's what I've been told about this HV area:

If you are doing 60k or more at 20agl, you will be at a nose down attitude. And if the engine fails, you'll initially drop a few feet (simply reaction time), plus the nose will want drop even further, too. Then you'll be too close above the ground to flare without slamming the tailrotor into the ground.

 

at 40ft and 60 knots, you'd simply do the final part of a normal straight in, starting with the flare.

[Gomer Pylot]

It depends a lot on what's below you. The h/v diagram assumes a flat, level, firm surface, such as a runway. Anything else means you're in the avoid area for longer. Flying in the avoid area in front of the 'knee' isn't the smartest thing you could do. At normal altitudes, a successful auto should be possible, assuming there is a clear area in which to land. If there isn't, you should have been at a higher altitude in the first place. Judgement is required at all times when flying.

[Goldy]

at 40ft and 60 knots, you'd simply do the final part of a normal straight in, starting with the flare.

 

And therein is the key...if you maintain that airspeed, and just that 40 -50 feet of altitude its doable. IF you let that airspeed bleed off as you climb away on a normal takeoff, and find yourself at 40 feet and 40 knots, it will be an interesting trip down. On a normal take off I watch airspeed more than anything else.....except maybe the jets I am avoiding at the time.

 

Best place to practice an R22 low altitude auto is at the safety class..

 

Goldy

Edited September 21, 2007 by Goldy

[Gomer Pylot]

I spend a lot of time in the avoid area of the h/v diagram, far more than I would like. Why do all hospitals have really high power lines all around their pads, except for the side that has the 15 story building? Scene flights almost always involve being inside it. Airspeed is life, and I get it and maintain it as soon as I possibly can, no matter what is under me. But the low altitude/high speed area is a place I just never even consider going into. Why would a reasonably prudent pilot ever do that, outside the military, where there may be more pressing danger to avoid?

[Scott83]

Unfortunately,

 

Helicopters are used more times than not in the shaded area of the H/V diagram. It's generally the area

that nothing else can do the job, except the helicopter.

 

Each aircraft and mission has it's own areas of danger and it's extremely important to understand them.

The Bell 206 has a high inertia rotor system, so it takes longer to lose that RPM, but when you lose it, it's

extremely hard, or impossible to get it back. The MD500 rotor system has a lot less inertia, so it's easy to

lose RPM, but you can get it back quickly. These are all considerations to make, along with the type of

work you are doing.

 

When I was doing powerline survey work, I worked for two different companies that had two different

techniques of doing the surveys. One had me fly about 100ft above the lines, at about 45kts and the

other company had me fly at 70kts and as low as I would get. The 45kt company always thought I was

nuts to do the 70kts low level, but in my opinion, it's safer (for engine failure purposes anyways).

 

At 45 kts and 100ft above the lines, you do not have much for energy stored in the system. This limits

your time to react to the situation. At 70kts, I wouldn't touch the collective, but do a cyclic climb and

once the airspeed bleeds down, I would drop the collective and set up for my landing area.

 

So the point I was trying to get to through my ramblings is that most jobs with helicopters will put you

in the H/V diagram for either a very long time, or short time depending on the job. Take the time to

think about your aircraft, the specific job you're doing, and how you would react to certain situations

that may come up. The more time you take, the better you will be prepared for murphy's law.

 

 

Fly Safe,

 

 

Scott

[nsdqjr]

Unfortunately,

 

Helicopters are used more times than not in the shaded area of the H/V diagram. It's generally the area

that nothing else can do the job, except the helicopter.

 

Each aircraft and mission has it's own areas of danger and it's extremely important to understand them.

The Bell 206 has a high inertia rotor system, so it takes longer to lose that RPM, but when you lose it, it's

extremely hard, or impossible to get it back. The MD500 rotor system has a lot less inertia, so it's easy to

lose RPM, but you can get it back quickly. These are all considerations to make, along with the type of

work you are doing.

 

When I was doing powerline survey work, I worked for two different companies that had two different

techniques of doing the surveys. One had me fly about 100ft above the lines, at about 45kts and the

other company had me fly at 70kts and as low as I would get. The 45kt company always thought I was

nuts to do the 70kts low level, but in my opinion, it's safer (for engine failure purposes anyways).

 

At 45 kts and 100ft above the lines, you do not have much for energy stored in the system. This limits

your time to react to the situation. At 70kts, I wouldn't touch the collective, but do a cyclic climb and

once the airspeed bleeds down, I would drop the collective and set up for my landing area.

 

So the point I was trying to get to through my ramblings is that most jobs with helicopters will put you

in the H/V diagram for either a very long time, or short time depending on the job. Take the time to

think about your aircraft, the specific job you're doing, and how you would react to certain situations

that may come up. The more time you take, the better you will be prepared for murphy's law.

Fly Safe,

Scott

Edited September 23, 2007 by nsdqjr

[spencer]

A cyclic climb.....are you serious??

 

I guess we'll be reading about you on the memorial forum someday....

 

Not to start an argument but he is serious and that memorial forum comment is immoral and unacceptable.

[Worldcrime]

The cyclic climb makes sense, trade the extra airspeed for some altitude, enter the auto with more TIME with a better chance to find a spot.

 

Referring to someone's future in a memorial forum is in really bad form.

 

Richard

 

http://heli-wear.com

http://heli-safety.com

[Gomer Pylot]

The cyclic climb may or may not be necessary, and usually not for very long. The avoid area for low and fast isn't very high - probably 10 feet or so for most light helicopters. It all depends on what you have ahead to land on.

[FauxZ]

So, at the risk of thread creep, what course of action would you take in certain areas of avoid curve? It's one of those what if questions asked among instructors at my school during the winter when we practice max performance. For practice, the maneuver is done to 50' (in summer I'm personally lucky to see 10' with a student)

 

Assuming the engine craps out at 50' (R22), what is the best option? Try to pump the collective a couple of times in a very nasty hover auto?? Or lower the nose and try to get at least some A/S before raising with hopes of slightly less disaster from translational lift?? Either way will hurt, what might hurt less? old timers, your thoughts???

[Gomer Pylot]

First, I've never been inside an R22. That said, I would probably lower the nose, lower the collective at least somewhat, get what airspeed I could, and pull everything I had at the bottom. That's what works in the 412 and S76 sims. It always depends on what you have under and ahead of you - some things hurt you more when you hit them than others. If it's a building in front, it probably will hurt less to go straight down and hit skids first. There is no one answer, you just have to play it by ear.

Edited September 23, 2007 by Gomer Pylot

[FauxZ]

Since this is training, they are almost always done at the airport on the runway. Since we don't have a sim, no one has been able to test the theory. Seems pretty split between airspeed and straight down. Thanks for the input.

[Scott83]

After reading nsdqjr's post, I thought I'd better reply.

 

1. I do think your comment "I guess we'll be reading about you on the memorial forum someday" was very tasteless

and unprofessional.

 

2. The second comment "A cyclic climb.....are you serious??" I would like to say, yes, I'm serious. In most other

missions I'm doing, I wouldn't attempt, or need to. With the circumstance of an engine failure low level over

powerlines at 70kts, there is no other option than to utilize the energy stored in the airspeed to climb a little and get

away from the powerlines. I wouldn't bleed off all of the airspeed, but enough to climb slightly. How much or how

little airspeed entirely depends on the specific circumstance.

 

As I said in my last post, each aircraft and each situation will require a different technique. It's very important to

spend time thinking about what you are doing with the helicopter and how you will react to certain situations. If

you haven't already, pick up a video from the Robinson Safety Course. They do a great job discussing rotor energy.

Take what you get from that video and put it to different scenarios that you encounter while flying. Last but not least,

try to stay out of the H/V diagram as much as possible. Only be there when you have to.

 

I encourage any constructive criticism, disagreements, or comments if they are professional, unlike nsdqjr's

comments.

 

 

Fly Safe,

 

 

 

Scott

[nsdqjr]

After reading nsdqjr's post, I thought I'd better reply.

 

1. I do think your comment "I guess we'll be reading about you on the memorial forum someday" was very tasteless

and unprofessional.

 

2. The second comment "A cyclic climb.....are you serious??" I would like to say, yes, I'm serious. In most other

missions I'm doing, I wouldn't attempt, or need to. With the circumstance of an engine failure low level over

powerlines at 70kts, there is no other option than to utilize the energy stored in the airspeed to climb a little and get

away from the powerlines. I wouldn't bleed off all of the airspeed, but enough to climb slightly. How much or how

little airspeed entirely depends on the specific circumstance.

 

As I said in my last post, each aircraft and each situation will require a different technique. It's very important to

spend time thinking about what you are doing with the helicopter and how you will react to certain situations. If

you haven't already, pick up a video from the Robinson Safety Course. They do a great job discussing rotor energy.

Take what you get from that video and put it to different scenarios that you encounter while flying. Last but not least,

try to stay out of the H/V diagram as much as possible. Only be there when you have to.

 

I encourage any constructive criticism, disagreements, or comments if they are professional, unlike nsdqjr's

comments.

Fly Safe,

Scott

 

 

Get over it.

 

Flying helicopters is dangerous, and you're guaranteed to lose a few close friends in this industry before all is said and done. If you don't like it, go be a florist somewhere. I'll take straight talk over sweet garbage any day of the week.

 

Helicopter 101: When the engine quits the nose is going to yaw and drop and you're going to lose RRPM, to varying degrees depending on the type of aircraft. You're saying that at 70KIAS you're going to leave the collective alone and climb using the cyclic hoping to buy more time. First of all, you don't fly your way out of the H/V Curve AFTER the engine quits. Second, CLIMBING in an auto is absolute suicide. 70 KIAS is a pretty good power off airspeed for almost any helicopter. You said watch the video from Robby. Well, I have, and if you watch the scene with the FAA pilot attempting an auto from 100' you see how little time there is to react. Frank even says that below 100' there's not much time to flare, much less CLIMB then enter the auto.

 

Three sources of energy: Airspeed, Altitude, RRPM. At 100' you have very little altitude, why the hell would you even consider giving away 70 KIAS of Airspeed energy??

 

Young pilots: don't even think about attempting this. Lower the collective like you're taught, get the ship level, IF you have time flare, if you don't then pull at the bottom.

 

You go ahead and sugar coat all you want, in terms of what might kill me, I'll take harsh words anyday.

[helonorth]

Get over it.

 

Flying helicopters is dangerous, and you're guaranteed to lose a few close friends in this industry before all is said and done. If you don't like it, go be a florist somewhere. I'll take straight talk over sweet garbage any day of the week.

 

Helicopter 101: When the engine quits the nose is going to yaw and drop and you're going to lose RRPM, to varying degrees depending on the type of aircraft. You're saying that at 70KIAS you're going to leave the collective alone and climb using the cyclic hoping to buy more time. First of all, you don't fly your way out of the H/V Curve AFTER the engine quits. Second, CLIMBING in an auto is absolute suicide. 70 KIAS is a pretty good power off airspeed for almost any helicopter. You said watch the video from Robby. Well, I have, and if you watch the scene with the FAA pilot attempting an auto from 100' you see how little time there is to react. Frank even says that below 100' there's not much time to flare, much less CLIMB then enter the auto.

 

Three sources of energy: Airspeed, Altitude, RRPM. At 100' you have very little altitude, why the hell would you even consider giving away 70 KIAS of Airspeed energy??

 

Young pilots: don't even think about attempting this. Lower the collective like you're taught, get the ship level, IF you have time flare, if you don't then pull at the bottom.

 

You go ahead and sugar coat all you want, in terms of what might kill me, I'll take harsh words anyday.

 

I have also thought about this situation since early in training. I think the original poster has the helicopter already inside the avoid area where if a control input not made, the helicopter would hit the

surface at a high rate of speed. Am I right? Would you lower the collective at 10-30 feet? You have a

choice of slamming into the ground or trade some airspeed for altitude and get the thing slowed

down to where you can flare and have at least chance to live to tell. Maybe you would lower the

collective. You would have plenty of RPM when you begin cartwheeling across the surface. Then

we would be reading about you in the memorial section. As an aside, you can save the "straight

talk" about how "dangerous" helicopter flying is for the bar.

[Scott83]

Nsdqjr, well obviously you haven't done survey work low level, or ag work for that matter.

 

Your autorotation would put you right inside the wires.

 

Also, from your post, you are assuming that I would try and get out of the H/V diagram and

that's not the case at all. I would try for a little altitude to get away from the wires and hope

for the best at the bottom. In a 206, you can successfully auto from 45kts as long as your

RRPM is good.

 

Again....it all depends on the helicopter, the mission, and the specific situation.

 

I would much rather try and buy a little time and establish an auto then fly into wires.

 

That's just me.

 

 

 

Scott

[zemogman]

You could just stall the blades and stradle them in between the wires...I mean c'mon they're not metal so you won't get shocked and it will be kinda cushiony with all that play in the wires...you could also slide all the way to the next pole...that should help slow you down...

 

I know, I know...sometimes it just takes a student pilot to figure things out...

 

I pray we never read about anyone on this forum in the any memorial thread...it's not about straight talk, it's called tact!!!

 

By the way...don't move too much while you're hanging between the high tension power lines...the blades may not withstand it then you definitely don't have any inertia left to autorotate...Of course if you buy heavy duty oleo-dampers ????

[Goldy]

You could just stall the blades and stradle them in between the wires...I mean c'mon they're not metal so you won't get shocked

 

 

Not sure which blades you are flying, mine are metal. Aluminum actually with stainless steel leading edges.

 

Maybe your thinking of a $10 million dollar ship with carbon fiber blades?? or an old Bell 47 with wood ones ?

 

Im confused.

[zemogman]

Oops...I thought they were composite material...they look like composite with metal or steel edges...I'm flying in the Schz.300C.

 

Either way...the entire post was a joke...I hope you didn't think I was serious about hanging the helicopter between the powerlines on stalled blades...I'm inexperienced, not incompetent.

 

Hope you're not confused anymore and all is well on the west end of the world...