Time to lower collective in event of an engine failure
 

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It mentions that all certified helicopters should have a published time to enter auto-rotation before catastrophic loss of rotor rpm. I haven't come across these figures before. A Google search reveals only 1.6 sec for the r22 and 4 sec for the r44:

Robinson R22 (with some comparisons to the R44)

This slide states 2 seconds for the AS350:

http://www.ntsb.gov/news/events/2013...esentation.pdf

Odd figures in themselves, can anyone verify these?

I was interested if anyone could post published times for other aircraft?

1.2 seconds for an R22

It clearly depends on the flight condition. In an R22 at 90kts you can maintain rpm with cyclic flare alone for over 4 seconds, I'm sure Dick Sanford said many more than that highlighting the importance of flaring the aircraft on entry as well as lowering the lever in a controlled manor.

And with a progressive flare extend that to 5 seconds

I remember, many moons ago, an Army pilot told me that with the Westland Scout, in order to maintain rotor rpm you needed to lower the collective about two seconds before the engine failed!

I would like to see anyone, with an unannounced engine failure not lower the collective for 4 - 5 secs, you will have catastrophic rotor stall.

Test pilots will never give you an exact figure for that time delay, because it will mean that they have died.

The nearest they will give you is the longest survivable time it has been delayed for.

In the civil world, for the portion of the H-V curve that is above the knee (i.e. youre in level flight), a one second delay is used from time of engine failure until the collective can be lowered. The cyclic and pedals can be moved immediately (the logic is that you might not have your hand on the collective, but it would be extremely unlikely that your right hand would be away from the cyclic, or feet off the pedals). From the low hover point to the knee, there is no intervention time, based that you should have your left hand on the collective - but also note that takeoff power is used for this portion.
For the military, a two second intervention is used for all controls. A life time!!!

This would depend on a lot of different factors, wouldn't it?

If my engine fails while I am descending at 25% Q, I could probably just leave the collective where it is. If I am in an OGE hover at max gross weight, not so much. If I am in an empty machine pulling 100%, climbing a couple thousand feet a minute at low forward speed, I might be in trouble even if I get the collective down right away.

4 seconds for the R44 seems rather high now. I found this graph while looking around:

http://cabri.co.nz/wp-content/upload...uto-rotate.jpg

I think the text at the bottom goes something like...

t/k is the criteria used worldwide to qualify an helicopter autorotation ability. It is calculated by dividing the usable inertia to rotor stall by the hovering power. t/k give you an idea of the time to land? (in a hover) or time to enter autorotation (in cruise) after an engine failure at full-power. Above values are given at sea-level std day.

Interesting that the subject of the original article, the 350, shows up quite well on that graph, especially compared to the 355. Also a shame the 206 isn't on it.

Not sure why the 350 should be better than the 355. The blades are identical(B2/B3 at least). Of course, the 355 is heavier, but with same weight they should behave identically.

B2 and B3 are similar but unfortunately NOT identical as some have already found out.

Hilico, if you look a little bit closer on the graph you will see a B406, I believe they meant B206. Never heard of a Bell 406.

JD

JD,

Bell 406 aka OH58D Kiowa Warrior. Bit like a 206 with some 407 parts.

Correct. Of course I was just making sure you were up to speed with this graph RVDT. :rolleyes:

Thanks

JD

TK period.
 

I'm not certain, but I think the TK time chart was the one produced by M Guimbal for his Cabri G2 publicity, being the occasion I completed an air test for an article for LOOP circa 201O ish. I've used the acronym ever since, but no doubt it is one of those terms that has been in existence for many years but largely forgotten.

New subject: AAD air show at SA Air Force base Waterkloof last week ... I completed a series of MD 530F displays at the show and wonder if any PP'rs were there for a critique. The show was of Farnborough proportions and even featured the first public flight of the Paramount Group's New AHRLAC multi role prototype.

Take care all. Dennis K.

Dennis

Are you now officially "retired" now as a display pilot as I think I recall you saying that Waterkloof was going to be your final one?

If so, may I wish you a long and happy retirement!

MB

Pilot's Post - Online Aviation in South Africa
To see DK vid scroll to bottom of page

Elusive retirement.
 

Mainly for MB ... well yes, I have to say the Waterkloof AAD show in South Africa was probably the best I've been lucky enough to attend. I'm told they had a 130k crowd most days ... and following my display, I felt a bit like the Pope addressing the wall-to-wall crowd from the commentator's balcony.

Flying the 650shp MD530F was simply majestic and I'm still running through the day's manoeuvres in my head. So much satisfaction from a good display and in the sunshine with a DA around 7-8k feet (and getting paid to fly) so I keep asking myself why anyone would retire from that situation. I'd also like to think the later Enstrom 480B display was technically as good as anything I've ever produced ... so dear pps, I plan to fly for one more year thru to the end of 2015. Did I say that last year?

Mind ... I think I may take up drugs ... just as addictive and cheaper! (only joking!)

But to close I can only say again what a superb handling machine the old Hughes company produced way back when and the latest 530F stump puller is a display pilot's dream. What on earth does the 540 fly like? Now I'm going sentimental!

Bye for now ppruners .. fly safe and warm regards to all. Dennis K.