[S-92] Autorotation Video

[CS-Hover]

the quote says "S-92 performing full power off touchdown autorotation landings at max gross weight. Two were performed that day. The engines are running but idle"


S-92 helicopter autorotation (power off landing) (http://www.youtube.com/watch?v=4JqmoWAhv5g)

high nose up , but still long ground run, at least in the second shot
any thoughts?

[Bravo73]

Those autos were performed as part of the certification process.

These vids have come up before so if you do a search, you will find some comments from a certain Nick Lappos (who was S92 Project Manager at the time, I believe.)


HTH

[BlenderPilot]

You asked for "any thoughts", well in my very limited thought process I can only say that with a little practice I'm sure those would be performed a lot better than what is shown in the video . . . . :)

[NickLappos]

Blender is absolutely right, and there is no need to practice when all you have to do is land from autorotation to meet the FAR/JAR. Also, the 92 is a Cat A twin, so a full auto is a pretty rare occurrence, and the crashworthy fuselage (almost like a Black Hawk) plus the basic autorotative capability should be quite satisfactory.

[psyan]

Nick tapped away: "the crashworthy fuselage (almost like a Black Hawk) plus the basic autorotative capability should be quite satisfactory."

Let us hope that in the unlikely event, the crew manage to be near a nice flat runway.

[NickLappos]

psyan,

Don't judge based on one set of autos filmed for posterity!

The 92 and the 76 at high weight have somewhat similar autorotation characteristics, and the 76 has (unfortunately) been in a few quite successful autos with fleet pilots at the wheel.

For the sake of all of us, keep hoping, however, no real dual flameout is fun.

[CH274]

Let us hope that in the unlikely event, the crew manage to be near a nice flat runway.
In an ideal world that would be a dream, having a routes lined with runways... but far from it. More likely routes lines with choppy sea water ;)

[Lutefisk989]

while the S92 is approved as a Cat-A twin, it was also approved for Category B. hence the requirement to demonstrate a full touchdown autorotation for certification, since engine isolation requirements can't be guaranteed for Cat-B...

[NickLappos]

lutefisk,

Unless you get out a cutting torch and hack saw, with the S-92 you get the engine isolation as part of the design!

And you are wrong, EVERY rotor craft must demonstrate a satisfactory autorotative capability, not just Cat B rotor craft. Just as the S-92 has done.

[Tweedles]

psyan said,

"Let us hope that in the unlikely event, the crew manage to be near a nice flat runway."

The EOL landing requirements for both FAR 27 and 29 helicopters only require the following (from AC27-1B, FAR 27.75 and AC29-2C, FAR 29.75):

"Demonstrated compliance with this requirement is intended to show
that an autorotative descent rate can be arrested, and forward speed at touchdown can be controlled to a reasonable value (less than 40 KTAS is recommended) to ensure a reasonable chance of survivability for the all engine failure condition."

The notion that a no ground-slide EOL can be easily accomplished, especially at the higher DAs, could indeed bite someone not used to those conditions.

[Thomas coupling]

Still a shoddy landing.

[Lutefisk989]

Nick: not sure I need a cutting torch...

the S92 has a limitation that allows use of cross-feed ONLY during Cat-B ops. am told this is because of the cross-feed valve design, which could result in flameout of BOTH engines if the cross feed valve fails. since this represents a single-point failure resulting in loss of both engines, it isn't allowed for Cat-A (that is, there's no engine isolation during cross-feed).

autorotation isn't considered an acceptable means of landing for Cat-A cert...so don't think full auto landing is required if the aircraft is FULLY certifed for Cat-A. stabilized flair/arrest probably OK for full Cat-A, as Tweedles alludes.

all that said...I think the autos in the video are impressive...it's a BIG aircraft to auto. land it level, and you'll walk away.

[NickLappos]

Lute,

I've been doing this for a while, so bear with me.

The crossfeed mixes one fuel tank's gas into both engines, which is true of all aircraft, and that makes use of crossfeed a cat B operation for any helo. Cat A separation defined in 29.903 says there must be total isolation of the two engine/fuel systems:
(b) Category A; engine isolation. For each category A rotorcraft, the powerplants must be arranged and isolated from each other to allow operation, in at least one configuration, so that the failure or malfunction of any engine, or the failure of any system that can affect any engine, will not—
(1) Prevent the continued safe operation of the remaining engines; or
(2) Require immediate action, other than normal pilot action with primary flight controls, by any crewmember to maintain safe operation.


Regarding autos, all rotorcraft must make at least one full stop auto to the ground, or else there is no type certificate issued.



§ 29.79 Landing: Category A.

(b) It must be possible to make a safe landing on a prepared landing surface after complete power failure occurring during normal cruise.



Thomas,

Not a nice thing to say! The next time an experimental helo needs touchdown autos, for the first time, with no practice, at maximum gross weight, in nil wind and with the entire world watching (including folks years later who make pot shots), maybe we'll ask you to do it! The number of ExP's injured in autos and HV curve landings is appreciable, even for pilots with 10,000 hours and 25 years of test experience.

[Lutefisk989]

Hi Nick:

Totally agree with what the rule states...but the associated advisory material (which is now 29.75, btw) allows other means to demonstrate compliance--

The intent of this rule is to demonstrate controlled touchdown conditions and freedom from loss of control or apparent hazard to occupants when landing with all engines failed. In these cases compliance can be demonstrated by leaving throttles in the idle position and assuring no power is delivered to the drive train. Also, computer analysis may be used in conjunction with simulated in-flight checks to give reasonable assurance that an actual safe touchdown can be accomplished. Another method may be to make a power recovery after flare effectiveness of the rotorcraft has been determined. Other methods may be considered if they lead to reasonable assurance that descent can be arrested and forward speed controlled to allow safe landing with no injury to occupants when landing on a prepared surface with all engines failed. ...

So if I were lawyer parsing this, I wouldn't require a full touchdown...

I see your point with regards to engine separation and Cat-B. But that raises an interesting question: Why allow cross-feed at all, except for emergency operations? Operationally, allowing crossfeed for only Cat-B means it could only be used is when the aircraft is configured for 9 pax or less (I presume VIP configuration)... I'll have to muse that one.

[JimL]

Lute,

An interesting discussion because it mixes the two concepts of Certification and Operation (as may the S92 RFM); consider this, when an S92 is cruising at 10,000ft with 19 passengers and large amounts of fuel such that it cannot meet a 50ft/min ROC, under what conditions is it operating.

Alternatively, under what conditions is the S92 operating for take-off and landing on a helideck (in the tropics)?

Jim

[MightyGem]

I've been doing this for a while
Understatement of the year, I think.

[CS-Hover]

JimL

i never saw the S92 RFM (but i liked to see it :O section 2 and 5 could be enough to me :O anyone??
so i can be wrong
but, if it's possible to drop some fuel, and/or passengers (ok, the last one, maybe they don't like so much :) ) or drift down to some altitude were the requirement of ROC can be meet, i think will be on PC1 (on JAA land)

helideck in the tropics?? :ugh: maybe, thanks god, there isn't JAA land there ;)



and from my very limited(very in did :() experience, there are a couple of "problems" that can need a "fixing problem" autorotation , even when both engines (both can be 2, 3, ...) are working 100% perfect
pilot experience apart (from the guys that flown the helicopter in the video), what catch my eye (and my asking comment) was the long ground run, even for that high pitch up attitude (lots of horizontal lift vector pointing backwards)

i've tried to find videos from other (similar size) helicopter, so it doesn't turn in "all against S92" thing, but without luck :*

[Tailspin Tommy]

CS,

I agree with you reference the long run-on distance after the deceleration high pitch attitude. Nick can probably offer a more articulate answer; however, the answer to stopping or significantly reducing the ground run distance at touch down is to perform the autorotation similar to the way the US Coast Guard used to teach the manuever for the H-52 (S-62 civilian version).

The coast Guard had a full instrument package and radio altimeter, which were all necessary to properly perform the maneuver. The decelration would start at 200 feet AGL, as the airspeed decreased below 50 knots, the nose was leveled with the horizon. By this point the aircraft was somewhere around 50 feet off the water, The pilot had to control rotor rpm by reducing collective as the nose was being leveled. At an appropriate point above the ground (as I vaguely recall 20 to 25 feet) the rest of the collective pitch was positively nicreased to allow the aircraft to settle in the water without forward airspeed.

We used to do the same manuever with our S-62s in the GOM, but wuithout SAS or radar altimters. The maneuver is a cheap thrill on the first try, but it works. We modified the maneuver to reflect more of a profile like the US Army would perform with the UH-1H (B205). Deceleration somwhere around 75 feet, hold to 30 feet, take out most of the decelration attitude and tounchdown in the water with an approximate2 degree pitch up attitude. Same result and still floating.

Army pilots rule!

Nick,
Any suggestions on an autorotation profile to the water to minimize forard movement on landing?

[NickLappos]

This thread is an example of why you dont see and hear more from test teams and why nobody releases video.

The video shows two autos, the first done in the type. From this, this group has focused on one aspect, the ground run, which was not optimized, because it did not have to be. I will bet nobody who has posted here has ever autorotated a 10 ton helo at max gross weight to the ground, and I will bet nobody here has seen any such auto done by any other such helo, but the thread moves on, regardless!

The auto capability of the typical large helo is about like the 92, in fact the 92 is probably better than most in its size range. It can be stopped and it can make a good auto entry to the water, but the test pilot on that day was just trying to land without harming a $100 million asset! Had he bent that machine, the program would have been set back by at least 6 months, and he would also have had visitors while in the hospital. He did a great job, and you got a peek into the test world. Deal with it!

[Graviman]

Albeit not helicopters, i can vouch that testing any vehicle exposes the machine to difficulties that might not have been anticipated. Serious respect to crew for having the guts to do it in an untried, and very expensive, prototype.

Interesting discussion about Cat A / Cat B. As a powertrains man i still wonder about the tail rotor drive. This is not a pot shot at any helicopter, but i do wonder how long before there is an electric motor or two with power taken from generator for each engine. TR failure is another situation requiring autorotation, and there is only one drive. E-drive fits right in with FBW.

[Robbo Jock]

Graviman,
At the risk of taking the thread somewhat off-topic, if you had electronic drive for tailrotors, would you control tail rotor thrust by varying RPM or pitch or (probably) a combination?

[Tailspin Tommy]

I think you are right, Nick.

This thread is in a death spiral.

Let's talk about real flying.
Dual engine failure calls for the following procedures:
1. Full left pedal
2. Monitor the OAT gauge
3. Recalling the reported surface temp durng flight planning, pull all the pitch you have when the OAT is 2C above forcasted. This is of course to account for the lag in the OAT gauge.

This King Bee Lead. I go now!

[JohnDixson]

Dear Thomas:

Not sure I understand what "shoddy" means.

Over the years at Sikorsky, I made the first power off touchdown autorotations in the UH-60, the SH-60, the S-76A and the S-92. Along the way, I had to teach the US Army team doing the evaluation of the S-67 Blackhawk how to do autorotations to the ground as a part of their evaluation. That hadn't been done before either.

Point is they all look pretty much alike; no dents, no dings, and all landing gear and structural loads well within limits.

Best of all, the meat wagon went back to its parking place empty.

If that is shoddy, its for me!

John Dixson

[JohnDixson]

Dear Lutefisk989,

Your note is absolutely correct, but during development/certification testing, the simulation tools are simply lagging the whole process and nowhere near in the state to convince anyone as to their validity in assuring that a replication of the entire autorotative landing would be valid. In fact, at certification we were still using flight test data to update/upgrade/modify the Flight Safety S-92 simulation, not the other way around.

So in reality there was not much choice: the landing had to be done.

Thanks,
John

[Thomas coupling]

Must be due to two things then:

(a) It must be an Army/Airforce thang - naval aviators don't do shoddy.

(b) Must be a yankee thang.

:ouch:

[Whirlygig]

Not sure I understand what "shoddy" means.
Shabby, shonky and other words beginning "sh" :} i.e. inferior.

Cheers

Whirls

[Heliport]

'Shoddy' means badly done, which clearly doesn't apply here for the reasons Nick Lappos has explained.

[Tweedles]

I did not communicate my intent very well in my last post. As Nick indicated, the regs to not require a "no-ground run" EOL. The ACs recommend a touchdown speed of <40 KTAS. I have had the privilege to be involved with these types of tests (FTE), and the slide can go on for many seconds/feet. Result? Skid shoes and skids: Worn out. Test: Passed. Steak dinner and beverages afterward: Well-deserved.

[Brilliant Stuff]

As far as I am concerned test pilots are GODS. :ok:

[RVDT]

ET Pilots ARE Gods.

PT Pilots just THINK they are!!

:O

E = Experimental
P = Production

[Graviman]

Point is they all look pretty much alike; no dents, no dings, and all landing gear and structural loads well within limits.
Hear,Hear. If i had been a design engineer on that program i would feel a great sense of relief that the TP had the experience and skill required to perform the test AND take care of a machine that i had lost many nights of sleep over.

RobboJock, the most successful engineering developments are ones which come of their time. I suspect TR e-drive would initially sit as a back up to a mechanical system. This might later evolve into the ability to break the mechanical link and reduce Ntr in case of hub problems. Later confidence might grow high enough to use two e-drive systems in place of the mechanical system. Then Ntr could be performance optimised.

[Robbo Jock]

Thanks Graviman.

[zebedee]

Tailspin
Just a question, did you perform this type of auto to the water in a real aircraft, or in a simulator?
Zeb

[Lutefisk989]

An interesting discussion because it mixes the two concepts of Certification and Operation (as may the S92 RFM); consider this, when an S92 is cruising at 10,000ft with 19 passengers and large amounts of fuel such that it cannot meet a 50ft/min ROC, under what conditions is it operating.

JimL: you're abosolutely correct about the integration of Cert with Ops requirements. Consider this: there is only one FAA operational rule (that I'm aware of) specifically requiring Category-A: Part-133.
When it comes to Cat-A, I think the folks who really "get it" operationally are the Europeans, because they must operate under "Performance Class" concept.
In this regard, I like how the JARs have effectively associated Cat-A with certification, and PC-1/2/3 with Ops (kind of like the difference between VFR and VMC, or IFR and IMC). Since the FAA hasn't adopted the Performance Class concept, Americans tend to forget that operating under Cat-A means three things: (1) you're within WAT limits; (2) you're using the published t/o and landing procedure; and (3) you can meet published obstacle clearance.
Oh, and to answer your question about 10,000': i dont' think it's operating under any conditions, with respect to Cat-A. When you parse the take-off and landing requirements for Cat-A, you'll see that it ends/begins at 1000' above the surface. Boy has performance planning become complicated, when you mix Cat-A/B with IFR!
JohnD: I'll say it again ... nice autos! :)

[Bushfire]

Just out of interest does the CH-53 undergo "power off touchdown autorotation" testing. That would be an awesome video.

[Tailspin Tommy]

Zebedee,

To the water. Did about 200 to 250 over a three-year period before we got rid of them. Used to take a B206 on fixed floats and do autos with all company pilots, once a year. All to touch downs on the water.

[NickLappos]

Bushfire,

It is a safe bet that every helo you have ever seen has been tested in auto to the ground. The 53 autos were done by a great TP at Sikorsky, Jack Peterson, who was a Corsair pilot during WWII. We kidded him that anyone who did a full auto in an H-53 needed a 53 to carry his gonads.

[topendtorque]

Hey Tailspin, Just a simple question. When you go down, does yer OAT’s go up or down????

As far as first on types go, my vote goes to Uncle Frank's’ lightweight blade first model. Tim tucker wasn’t it? No simulators or computer modelling there, Uncle Frank never owned a computer until recently they reckon, Just a slide rule and the back of a second hand envelope.

Somewhere recently someone was talking about exceedances, and then I saw a comment about power recovery in a S92.

Struth.

That reminded me of a cartoon that I vividly remember from my pre teens years. It featured Yogi Bear who had gotten mixed up in a knuckle-up with a real - big - bad - bear. Yogi got a smack in the mouth and the next picture showed Yogi with a real dumb surprised look on his dial, spitting out a stream of molars. Very funny I thought.

I could see the S92 driver just the same, dumb surprised look on dial, all the gears and turbine blades in a stream out the back, going west.

[mfriskel]

Lutefisk989 -
I would have to think hard about what is safer and even able to prove. If you accomplish an auto to a point in space, in a max gross weight machine, and are trying to prove ZERO rate of descent and acceptable forward speed, you will need to have DGPS, cameras filming the point in space ect.. When you perform the maneuver you will be flying that max gross weight machine to a point in space, performing a good flare, getting the forward speed (hmmm are we referencing ground speed with no wind via a GPS or relying on an airspeed indicator during a large flare) to an acceptable speed- then we will push forward cyclic to get the nose down to at least level if not an accelerative attitude, which will further decay NR. Now we will be getting the PLA back to the fly position, NR will be below normal and we will be re-entering autorotation while the engines are coming up to catch the NR. I think I like touchdown autos, and in the heavy ship I will take the groundslide/roll, at least I have normal pilot references to the ground, and am proving confidance in the machine design. You will also be accomplishing work-ups from faster touchdown to slower as you gain experience and probably will start at a lower gross weight at first as well as doing a few power recoveries in the flare during work-up.

[JohnDixson]

Thanks for the comment, Lutefisk.

You know the FAA required that we perform a power off landing as part of the S-76A cold weather certification. So we were flying at the Inuvik, NWT aorport and I was lucky to be flying with Jim Kay, who did the S-64 development and flew with Frank Tefft doing the CH-53E development. The FAA pilot could have insisted on doing this one, but chose to let us do it.

Anyway, these things are one-time events, and past success doesn't count.

So we came around the pattern, put the gear down and proceeded to do a "shoddy" power-off landing. I thought it was OK as we rolled forward, and then looked over at jim Kay who was laughing. "Come on Jim, it wasn't that bad" is what I recall saying. " No, John, it was fine, but I didn't turn the on-board instrumentation on, so you'll have to do another one" was his response!

[Mr Toad]

John and Nick: just for another red herring -

Do you think the 76C+ is capable of a zero-speed landing to the deck from a double engine failure? While practising the steep approach profile necessary for Cat A elevated heliport procedures I often wondered if you could manage it without any power input at all. Never dared to try though, and the sim was definitely not the place to do it.

I seem to recall doing touchdown autos during the BV234 type conversion with Boeing TP Dick Balzer at Prestwick. The flare started at 600' and you needed a loooong runway. What you did NOT need was collective, the whole thing was done on attitude and resembled a space shuttle landing; the flat underbody provided a real aircushion near the surface. Dick was so laid back he used to stick his snakeskin boots up on the coaming and tell you to get on with it... And yes Nick, the ECLs were fully retarded and I think the APU was started. Do Chinook pilots still do autos to the deck?