Full down auto from HV curve

[ABarnes]

Good recovery, good landing. The only thing I want to add that I haven't seen mentioned yet (sorry if I missed it) is that you keep mentioning "saving the helicopter" throughout your posts. I think it's important to emphasize that it's not just the helicopter at stake when bad decisions are made; it's your LIFE at stake. Bad decisions can kill. Yes, of course, if you save the helicopter you save a life or lives as the two are linked. But thinking in terms of damage to the machine and not damage to the person can possibly make someone a little less cautious than they should be.

 

Good job saving the machine and more importantly, yourself. Lesson learned.

[StanFoster]

Abarnes- I dont quite understand. I of course was trying to save myself. Saving the machine machine means I walk away unscathed also. I am trying to think of a scenario where saving myself would mean trashing the helicopter...but I cant think of one.

 

 

Stan

[Mikemv]

This autorotation was not done from inside the HV curve. I do not believe there is one for this helo as it is not a Certified aircraft. Stan could have done better by not lowering the nose, increasing the sink rate and having to deal with excess speed at the bottom. Doing a gentle flare, level and cushion without all of the ground run would have been better, especially staying over the grass with an oh so gentle turn.

 

Stan did a great job, accepting the situation and being a pilot and flying the helo until it stopped!

 

I doubt he had time in the 7 seconds to think about who or what he was saving. He did what he should have and flew the aircraft until it was on the ground and stopped.

 

I think he learned something as he has admitted. Life goes on and thoughts are not about lives and aircraft!

 

Best Wishes,

 

Mike

[StanFoster]

Mike- Not trying to argue here, but please explain why you think I wasn't in the HV curve? I was around no more than 100 feet off the ground and going around 40 mph airspeed estimated. Any HV chart I have seen shows roughly 200 feet and 50 mph would just be out of it. I don't want to dispute what I know is advice from a high time helicopter pilot, but how much time have you in a Helicycle? I know I am just a fledgling here, but I have developed a lot of feel for this helicopter by practicing different autos. My training and my gut feeling both told me to get more airspeed by lowering the nose. I had a feeling that I would have pancaked in had I just let it come down at such a slow airspeed. However, I will go up to altitude and practice doing such and see if I can stop the descent at the slower speed. My previous practice autos at speeds slower than 50 were not very satisfactory. You may very well be right, and I assure you if my tests convince me your way was better, I will certainly say it here. I have learned a lot and more importantly know I have a lot more to learn! Stan

[Shaun]

Seems like the ground was very flat, trading a high rate of descent for a faster ground-roll seems like a good idea in this case. And the proof is in the fact that the helicopter was undamaged, for an engine failure on takeoff no less.

[Mikemv]

Dear Stan, I do not think that you are being arguementative and I truly believe you have asked a valid question and why not ask a high time pilot for an answer?

 

Actually, I expected it, as too many pilots do not undestand the HV diagram, how it is created and how & when it applies. It is an area I address in my "C&E Seminars"

 

Let me first ask you if the Helicylce has a published flight manual or POH? Is there a Performance section/chapter in this POH? Is there an actual HV Diagram? If one does not exist, how could you be in it? Granted, common sense and previous training would give you ideas about safe operation and considerations for HV type areas.

 

HV curves for Part 27 Certified aircraft are developed thru testing and are formulated on a helo being at GW and Std. Atmosphere.

 

Altitude and Airspeed numbers/values are only two elements of an HV diagram!

 

Aerodymamics of the rotor system in a given state determine whether the AS and Alt. numbers come into play! Once you lowered the collective and the engine rpm tripped the shut off, there is no way you could be in the aerodynamic state required to be in an HV diagram.

 

Now, addressing increasing airspeed and rate of descent. Lowering the nose from 100 feet to gain so much excess airspeed only decreases rotor rpm. Getting to a flare height and not flaring to decrease ground speed, rate of descent and build rotor rpm is contradictory to the training I know you have had.

 

If you had entered a training autorotation from 1,000' and got to 50 feet with that same rate of descent and aispeed what would your actions have been? Not to flare?

 

I do not want to turn this into an Internet class on HV Diagram.

 

So everyone knows, I first sent Stan a PM with some congrats on a safe and successful outcome with some other comments. I know he flies as best as he can and we should all applaud that and also the fact that he shared this info with everyone here!

 

Sincerely,

 

Mike

[Mikemv]

Seems like the ground was very flat, trading a high rate of descent for a faster ground-roll seems like a good idea in this case. And the proof is in the fact that the helicopter was undamaged, for an engine failure on takeoff no less.

Shaun, trading HIGH rate of descent and EXCESS airpeed was not a good idea. What was to say that the ground was hard and that skid would not sink into the surface and roll the helo? What about sliding and catching a skid on the lip of the hard runway surface? If the helo had rolled on the initial touchdown on the grass with all of that speed, what would you say? He was going to fast? Why did he not flare?

 

Why not flare and accomplish what we should in a flare and have an advantage to a successful outcome?

 

Again, kudos to Stan for sharing all of this!!!!!! He acted like a PIC and flew the aircraft all way to the ground and then some and it worked out! This time. There was a better way!

 

Sincerely,

 

Mike

[Shaun]

Is there an actual HV Diagram?

 

Does the FAA require Helicycle to publish one? If they don't wouldn't it still exist, just not on paper. Does any single engine helicopter not have an HV zone? Would his T/O profile be in that zone, is the question, seems like it would.

 

Someone told me of a Bell prototype with extremely heavy blades that could auto from any AS/altitude condition, but lacked power, not sure if that is true.

 

I'm also still confused as to how the pilot can know the collective limit without a torque gauge. Could anyone elaborate?

Edited November 26, 2010 by Shaun

[Goldy]

Does the FAA require Helicycle to publish one? If they don't wouldn't it still exist, just not on paper. Does any single engine helicopter not have an HV diagram?

 

Someone told me of a Bell prototype with extremely heavy blades that could auto from any AS/altitude condition, but lacked power, not sure if that is true.

 

You Don't need a published and verified HV curve unless you are going for certification.

 

Yes, Bell did build such a ship. They called it the model 47 !

[Whistlerpilot]

Someone told me of a Bell prototype with extremely heavy blades that could auto from any AS/altitude condition, but lacked power, not sure if that is true.

 

I also heard about this, but haven't confirmed it. I was told it was an early 206 (possibly C-18) with lots of extra tip weights added. I was told it didn't have a HV curve. Could pretty much 0 airspeed auto from any alt.

 

You're right Goldy the 47 autos very well but still wouldn't want to do 0 airspeed from 100 feet. I personally know 2 pilots who had to do this (Hovering at the end of a 100 foot longline) in 206 and Astar who got it down with no damage.

 

I've practised engine failures in the hover from 35 feet in a 206. Not my idea and don't recommend it, but it's doable. That would be harder to do in a 47, and very detrimental in an R22!

[Whistlerpilot]

I'm not sure if this excellent US Army paper has been posted before but it's great reading about Mikemv's point. It's more survivable to contact the ground with no airspeed but some rate of descent rather than running into things with airspeed.

 

http://fireheli.com/Files/howtocrashahelicopter.pdf

 

Luckily Stan had a flat clear area to run it on but if that's not the case better to flare.

[Shaun]

That paper supports a running landing to avoid a hard impact if the conditions permit, given that it is easier to fly. Obviously when to do what is completely subjective and situational.

 

I wonder though if the Helicycle being a kit helicopter, would lack the same standard of vertical impact survivability of a certified helicopter, and favor reducing ROD as much as possible.

[Whistlerpilot]

Lots of food for thought. You're right Shaun every situation is going to be subjective and situational. I think it's worth going every different probability and pre-thinking how you would like to react. For example on approach at under 50' agl and less than 25 kts is going to be very different than 100' agl and 40 kts.

 

In the end Stan reacted to a bad situation and created a good outcome. Kudos to him for sharing his experience here. Wondering if anyone else has had a similar situation - engine failure low and slow, and would like to share?

[StanFoster]

I am enjoying the interest in this thread and am learning a lot. I am making changes on my turbine. The factory thinks its a good possibility that my upper fuel limit needs to be increased. They had another one that the turbine just pulled down from not having enough fuel. My belts are slightly over on their tension, it was 80 degrees that day, my weight at 220 is the max pilot weight, and I had just topped off all my tanks. So I was loaded to gross on a warm day, and was overzealous on my collective. What is senseless is that this Helicycle at gross weight just has so much power to weight ratio, that I don't need to use but 75% of the available power. Another device I am changing out is my main fuel solenoid. It will now not require a 12 volt circuit to keep the fuel on, instead it will now take 12 volts to shut the fuel off. I can lose both batteries and my KeyWest regulator will run all my electrical. I now also have a small backup sealed battery wired into the system to keep power going to the governor. This will keep the governor and the overspeed safe from a catastrophic power failure. This battery is wired with a diode isolating its power from only going to the governor, yet also being constantly charged. Many Helicycles are flying, and about half have the NC MFS like I had. There really have been only 2 MFS failures due to losing the 12 volts keeping it on. I just want to eliminate that possibility, and soon will have mine changed over. I have experienced a forced landing that I am thankful happened, but I am going to do my best to improve my odds by improving my machine, and improving my flying by flying safer. This has been a LOT for me to absorb in this short period of time! Stan

Edited November 27, 2010 by StanFoster

[Goldy]

I personally know 2 pilots who had to do this (Hovering at the end of a 100 foot longline) in 206 and Astar who got it down with no damage.

 

Yes, but you do gain some advantage from the N2 momentum helping you out...if you recognize the turbine loss immediately. Don't get that added help from a piston. Either way, I wouldn't want to be there!

[Whistlerpilot]

Very true, with the piston machines the RRPM loss will be immediate. Another advantage for the R66 which all ready sounds like a good autorotater.

[iChris]

Someone told me of a Bell prototype with extremely heavy blades that could auto from any AS/altitude condition, but lacked power, not sure if that is true.

 

I also heard about this, but haven't confirmed it. I was told it was an early 206 (possibly C-18) with lots of extra tip weights added. I was told it didn't have a HV curve. Could pretty much 0 airspeed auto from any alt.

 

Bell Helicopter completed Flight Test Evaluation of the High Inertia Rotor System (High Energy Rotor Systems - HERS) for the U.S. Army in 1979. Link:

 

The HERS has demonstrated the ability to reduce or eliminate the height-velocity restrictions on autorotational landings.

 

 

 

In the case of this experimental helicopter there was very little deceleration (flare) near the bottom, so there was minimal arrestment of descent rate or forward speed (i.e. extended ground run). However, there was sufficient kinetic energy remaining in the rotor system to arrest the rate of descent enough to allow a safe landing with the initial collective pitch pull.

 

This helicopter seems to have been designed with higher rotor inertia, low gross weight, low disk load, and excellent landing gear capability. All this and the pilot's reaction in getting the collective down early, allowed for this favorable outcome.

 

There is an Autorotation Index (AI) that is sometime used to compare autorotation performance. The higher the AI the better the autorotation performance: High rotor inertia vs. low gross (850 lbs. max) and low disk load paid off in this case (i.e. higher AI).

 

AI = (I_R* Ω²) / (2 * W * DL)

AI= (rotor inertia mass) x (rotor speed)(squared) / (2 x gross wt.)(disk load)

 

below are some of the factors that increase the favorable outcome of any autorotation landing. Some are built into the design and some you control.

 

Pilot technique.

 

Favorable headwind.

 

Favorable landing surface

 

Decreased gross weight.

 

Low-density altitude.

 

Low Disk Load (gross wt./rotor disk area)

 

Low power required to hover.

 

Increased rotor inertia (blade weight, tip weights, etc.)

 

Increased blade tip speed.

 

Increased blade area, which will allow a lower rotor speed before stall.

 

Increased capability of the landing gear.

 

 

It is possible to do better than published H-V curves. An evaluation by Systems Technology showed that preliminary tests strongly indicate that successful autorotations may be performed from well within the unsafe operating area of the height-velocity profile of a helicopter by employing algorithm that provides guidance training on control inputs. Figure 6 (page 10) of the report show safe landings with Bell 206L done from 100' AGL, zero airspeed. Evaluation of a Rotorcraft Autorotation Training Display on a Commercial Flight Training Device

Edited November 28, 2010 by iChris

[iChris]

Whistlerpilot, on 26 November 2010 - 15:16, said:

I personally know 2 pilots who had to do this (Hovering at the end of a 100 foot longline) in 206 and Astar who got it down with no damage.

 

Yes, but you do gain some advantage from the N2 momentum helping you out...if you recognize the turbine loss immediately. Don't get that added help from a piston. Either way, I wouldn't want to be there!

 

Not much the N2 can do to help... There's little or no momentum from inertia from a free turbine type engine like that installed in the Bell 206 and Astar. Moreover, there's not enough inertia from the power turbine (N2) to aid in maintaining rotor RPM after an engine failure. In fact, the piston engine gives the most noticeable warning.

 

The Solar turbine engine use in this experimental helicopter is a fixed-shaft single stage centrifugal /single stage power turbine. Not much momentum there. Can’t depend on a dead engine to help with rotor RPM.

 

However, Solar engines are dependable. Solar fixed-shaft turbines are used to drive the APU for electrical and hydraulic power on the S-64’s. We had few if any problems with their engines.

Edited November 28, 2010 by iChris

[Whistlerpilot]

Thanks for posting those article iChris. I learned a lot. I've never used a Frasca simulator but it sounds like the enhanced auto training in the HV curve using that simulator algorithm is a really good idea. It talks about more pitch variation than I've used and I wouldn't want to be experimenting if the real thing happened low and slow.

 

Do you know why the HERS was not put into production? Seems like the R22 could benefit from some HERS upgrades!

 

Great info, thanks again Stan for getting this topic started.

[StanFoster]

Whistler- Glad you are enjoying the extra life this thread has had. I am here more to learn, but when I can share some learning from a mistake I made, its only right. I have always been an envelope pusher. No matter what piece of equipment I am running whether it be a tool, a vehicle, or an aircraft, I seem to have to test its boundaries to find its limitations., then I back off and stay a comfortable margin. from then on. I will forever have this memory hard wired in my brain. I will probably take off like grandma from now on. I feel I have a fantastic little helicopter, and no, its not certified, but its my way of achieving having my own helicopter. I also push the envelope on not being afraid to share my shortcomings. I mean, come on, I am a fledgling helicopter pilot who knows I have a LOT to learn, and will NEVER learn it all. I am in awe of the levels of expertise here coming from you helicopter veterans. My feeling is that displaying what my euphoria did to my common sense may help us all keep those feelings in check. Stan

Thanks for posting those article iChris. I learned a lot. I've never used a Frasca simulator but it sounds like the enhanced auto training in the HV curve using that simulator algorithm is a really good idea. It talks about more pitch variation than I've used and I wouldn't want to be experimenting if the real thing happened low and slow.

 

Do you know why the HERS was not put into production? Seems like the R22 could benefit from some HERS upgrades!

 

Great info, thanks again Stan for getting this topic started.

Edited November 28, 2010 by StanFoster

[iChris]

Thanks for posting those article iChris. I learned a lot. I've never used a Frasca simulator but it sounds like the enhanced auto training in the HV curve using that simulator algorithm is a really good idea. It talks about more pitch variation than I've used and I wouldn't want to be experimenting if the real thing happened low and slow.

 

Do you know why the HERS was not put into production? Seems like the R22 could benefit from some HERS upgrades!

 

Great info, thanks again Stan for getting this topic started.

 

The old philosophy of "keep it cheap and keep it light" sometimes rules. It also comes down to compromises and trade-offs. Rotor inertia should be high for good autorotation characteristics. On the other hand, the inertia should be low for minimum blade and hub weight, low drag, and longer life limits/TBO.

 

The increase weight and the increase centrifugal loads at the blades and hub would require some modification. You could reduce the rotor speed ( v² ) to counter the centrifugal loads, but still some modifications at the blade maybe needed to make up for the required lift. CF (centrifugal force) = mv²/r

 

So they came up with a compromise range that the designed inertia should allow enough kinetic energy, after power chop, to supply the power required to hover for at least 1.5 seconds before blades stall, low end, and 3.5 seconds on the high end (HERS).

 

You can take the low inertia R22 up to a three-foot hover with the rpm top of the green, then chop and pull. You should be able to hold that three-foot hover of 1.5 seconds, hopefully. The Bell 206 falls in the two-second range.

 

The recommendations on page 112 sums it up; modifications of existing hardware or new design are needed. That's not cheap or light.

 

5.2 RECOMMENDATIONS

 

To fully assess the weight increase required for a High Energy Rotor System, a complete rotor design is needed to establish a weight for a production configuration. This program modified existing hardware to achieve high rotor inertia requiring both structural weight and aerodynamic penalties that are not necessary if new designs are made.

Edited November 29, 2010 by iChris

[GmeisteR]

WOW what INCREDIBLE FOOTAGE. you even managed to not hit a runway light honestly, regaurdless what what anyone says, you definetly did a GREAT job of saving yourself and the ship. My Thumbs are UP

[iChris]

Actually, I expected it, as too many pilots do not understand the HV diagram, how it is created and how & when it applies. It is an area I address in my "C&E Seminars"

 

HV curves for Part 27 Certified aircraft are developed thru testing and are formulated on a helo being at GW and Std. Atmosphere.

 

 

That maybe true, many pilots don't know much about the airworthiness standards for a HV diagram.

 

1. To learn more, read the regulation that sets the requirement for the HV diagram in normal category rotorcraft with maximum weights of 7,000 pounds or less and nine or less passenger seats, FAR 27.87.

 

2. Read Advisory Circular AC 27-1B That provides information on methods of compliance with 14 CFR Part 27, which contains the Airworthiness Standards for Normal Category Rotorcraft. It includes methods of compliance in the areas of basic design, ground tests, and flight tests.

 

After AC 27-1B downloads read pages B-37 thru B-45 (only eight pages) and you'll know more about HV than most. Can also be downloaded at the following link:

 

http://www.airweb.fa...u%20Chg%203.pdf

 

 

Also: Autorotations In The Bell 206 (Video)

Edited December 2, 2010 by iChris

[Mikemv]

Chris, as always, great info from you. The Bell video with Loren narrating and Gary flying is priceless. It was Gary and me that performed hover autos to 100' in both B206L and B407 Thank you, Mike

[StanFoster]

G-Meister- Thanks for the kind comments. I assure you I missed the runway light by accident , and if I were headed straight for it, I would not have attempted to avoid it. Just bowl it over instead of roll it over! ha

 

 

Guys.....I have been flying the last two days....and I have to be the most matured helicopter pilot over this incident. I am not the same pilot. My future videos on you-tube which I have over 65 of, will look like they were taken by another pilot...simply because they will be!

 

I want to again thank Mike for his tactful efforts on explaining to me that I could have still saved this helicopter over less desirable terrain than the smooth grass I was given, and do this by not gaining airspeed and better use of my collective. I still firmly stand by my statement that my skill level at this time would not have been able to pull off what I am sure Mike says he could of. I am sincere about this...and this will just put a catalyst in my belly to go out and say...."I want to be like Mike" Sorry Mike...I just had to say that and I am not poking fun, but respectfully saying I am listenting and wanting to get to your level.

 

I have a lot to learn, and I thank God for the miniscule skills I used to save my ship my way...and giving me the experience of my life, and the icing on the cake is I have a freakin video of this. I would have never told this story had I not been able to prove it....as I could just hear the eyeballs roll back in their sockets...and people muttering "yea...right".

 

Stan