Hopefully John will. But in the meantime you can work it out yourself, using Newton's equations of motion (it won't just apply to a SHAR, but to any body hovering at 75 ft):

Type 10H seat is zero-zero but altitude must be at least 10% RoD for a successful escape. Assume thrust goes from hover thrust to zero in an zero time. Assume aircraft falls at 9.81m/s/s i.e no atmospheric drag taken into account to counter the a/c and mother earth's attraction for each other.

You should get the same answer.

Of course, in reality no engine's thrust goes from hover thrust to zero in zero time, even if the engine explodes. And of course, the aircraft will fall at a slightly slower acceleration due to atmospheric drag.

I reckon those two factors should buy you a good 0.1 seconds.

Regards,

Nozzles

Morning chaps

Thank you jmgriff for your PM as I had not kept up with this topic.

For me there are two sides to these recent issues, the numbers game that nozzles has been addressing plus what you have going on in your head while you are hovering.

I know of nothing that makes me question any of nozzles calcs. I don’t recall hearing about 10% of RoD before but that is probably because I am out of date - it certainly sounds a reasonable point.

The problem with trying to work out the numbers is the four major variables around at the moment the seat fires:

Height
RoD
Attitude of the seat rails
The IAS into which the seat emerges

The flight path of the seat both before and during man seat separation is bound to be affected by the IAS, as well as the way the chute deploys and inflates after MSS.

As nozzles also pointed out the rate of thrust decay is pretty important too.

I had a sort of hunch that come the dying whine (or big bang) in the hover then it would be nice to know what trim change this would invoke on the aircraft due to front vs rear nozzle thrust decay rates and any torque changes. So I took a nice light jet back in 68 time and did a series of VTOs from the Dunsfold pit (to make the go as good as possible – it was always better without ground effect), then as it shot up through 150 or so feet I chopped the throttle back by ever increasing amounts on successive VTOs before quickly restoring it to max. I think I got down to about 80% on the last one. Doing this there was always a nose down and right wing down trim change. Nothing violent but that was the clear trend that developed. Nose down seemed good to me ‘cos that would put the seat rails closer to the vertical. Pity about the right wing down. Mind you by reducing throttle I was only simulating the dying whine case. A fan trying to seize or the HP spool ditto could clearly induce different effects.

Now back to ones head. In my time I admit to being a bit fatalistic about hover regime ejection. Not that I was fatalistic about any other flying matters – far from it. It seemed to me the seats fitted (and we had several in different early aircraft) were clearly getting better from the P1127 onwards and this was nice to know but I realised that it was not much use trying to predict whether one should eject or ride it down from a hover (both have been done successfully) as on the day one would doubtless do what seemed best at the time.

Indeed after doing the clearance of the then new yaw autostab failure cases which involved flying in jet borne circles at 30 to 50 kts and below 100 feet in the middle of the airfield, arming the failure box and then waiting for the yaw hard over to happen following a random delay between 1 to 9 secs, then stamping on the rudder etc, I was taken to task by Barrie Tonkinson (another Dunsfold tp) about ejection issues.

Barrie asked me whether I was primed to eject during this yaw stab stuff. I looked puzzled and said “you what?” or similar because the subject had never crossed my mind. My head was full of what I had to do and I had not considered failure on my part. The subsequent conversation made me feel that I would probably still be in the aeroplane when it hit during a handling related event as I would be too busy trying to recover the particular situation.

In other words I reckoned that because ejection was not something I routinely considered I would probably not recognise a sudden need to eject before it was too late. I was later proved wrong in this when as a passenger in the back of a two seater going off a skijump the nose rotated up and the right wing went down. I instantly thought ‘punch out’. My next thought was to look down at the controls and see if they were in the right position. They were not, so I put them where they should have been and the thing shook itself like a shaggy dog and flew away.

Nice talking to you

Regards

JF

John Farley

Can you relate the circumstances of Bill Bedford's Harrier ejection?

I was tempted to leave him behind once when I accompanied him in a dual Hunter during the sorting out of rudder buzz, which was awfully close to flutter, during supersonic pull outs. Four heavy feet were not enough to prevent it happening.

Change of mass balance in rudder system was the cure.

Milt

Bill ejected from a P1127, not a Harrier. On 16 Dec 601 he was flying XP836 conventionally when the front left nozzle detached. Hugh Merewether flying chase checked the RHS side and could see nothing wrong. Because of vibration Bill decided to divert to Yeovilton. When he put flaps down he could not control the lateral trim change resulting from the nozzle asymmetry so he ejected. As ever with hindsight, if Hugh had looked at both sides or Bill had pulled the flaps back in all would have been well. But there you go easy for me to say now.

I know what you mean about rudder buzz in the T7. I always reckoned it sounded like a Bren gun being fired down by your feet. Your experience pre-dated mine. By my time the fix was not a mass balance change but the ‘standard’ way of changing the rudder aerodynamics by adding a little spoiler to the trailing edge on susceptible aircraft. Overnight job for the nightshift.

Regards

John

http://img47.photobucket.com/albums/...r_buzz_fix.jpg

John Farley

Hunter 7 rudder buzz.

Thanks John for your post.

Have had residual concern over the continuing airworthiness of XJ 615's tail since I spotted it in a magazine a few years ago still in flying condition.

XJ 615 was the test aircraft for rudder buzz. If you know who has it now I think it would be prudent to advise that the fin/rudder be carefully inspected.

Perhaps I am still a bit twitchy over my survival of a main spar failure in a Valiant - XB 215 - second prototype.

Now back to ejection seats and ejections.

Did you know about Tony Svenson's (16 ETPS) ejection from the Mirage III at 850 Kts CAS?

I'm rarely for these "auto" things, but in VSTOL jet, suspect a good idea here.

A GR3 was lost at Witt early 90s after an HP blade failure in the hover. The ensuing rapid decay (instant?) of RPM, and the detached blade removing Hyd systems etc. made the "brick" calculation above pretty accurate. The pilot did survive, but very seriously injured, and heroic efforts by fire and medics to extract him.

From that date, whenever I approached the hover, I'd remind myself that at the first sign of Eng Failure, I'd have to be "out". Problem was if you tried to make any diagnosis, it would probably be your last thought! On the other hand, a loud noise, or warning etc could well be spurious or unrelated - not helped in the GR7 by all warnings being the same colour (no red v yellow warnings). No RPM or JPT "gauge" either - all digits, so hard to make a "snapshot" assessment. Fortunately never came to it...

So for JSF, if a reliable system detecting a substantial loss of thrust, whilst in the hover regime can be developed, a good thing. A few IFs though to tackle <G> or the inevitable headlines about £50M serviceable aircraft lost due malfunctioning auto eject thingy...

Following JF and NOD's posts, I hope the 'auto-eject' function has an attitude input of some sort!

I remember clearly (2 weeks before my MB tie) the unfortunate young Harrier pilot who had an uncontrollable roll control excursion in the hover at 50'. He ejected quickly but not before the roll angle was such to negate the vertical rise of the seat. The point being NOT that he could have survived staying aboard, but that the a/c attitude MIGHT be wrong for the moment of an 'auto' ejection and it possibly could be improved? In his case, of course, this auto function would not have been relevant since there was no engine problem.

We all tried the same failure in the sim subsequently, and found that the 'older and more experienced' you were, the later one ejected, trying to 'sort it out'. IMHO there is a definite argument for a correctly programmed auto function in the hover.

This may be senility creeping in, but I do seem to recall many years ago that developement was made on a gyro stablised seat that could survive (including occupant) a 100ft agl totally inverted initiation. I have a dim recollection of seeing the test rig on "Tomorrows World". Have my brain cells fried or was this ever developed further. It may have been tested for an A10 application? Anybody shed any light on this?

Maybe - assuming nil RoD and good IAS (see JFs post above).

If you now add in high RoD and nil IAS (VSTOL aircraft with Eng Fail) and a different kettle of fish <G>

The JSF automatic ejection seat will not be a first - the Yak 38 (Harrier-ski) in service with the Soviet Navy had such a seat. It was the same seat as a Mig-29 with a control system that in hover mode auto-ejected the pilot if rate of descent/attitude exceeded pre-set limits. I believe it saved the life of 30-40 pilots, some from situations where a human being could not have reacted fast enough - one of them during the first live ski-jump trials aboard the Kiev.

Sorry Worf - you popped up while I was typing! But here is my bit anyway.

The Russian Forger fleet had an auto eject system that their mates told me had a 100% success rate at low speed and about 30 saves (some two seaters). Because in the hover the front was held up by two lift engines and the back by the vectored thrust main donk they had no option but to fire the seats on auto if the pitch attitude varied by 5 deg from that in the hover. By the time they got to the Freehand the seats were better and they allowed a 10 deg pitch change before boom. IIRC the roll figures were 10 and 20 for the two types. I would suggest the F-35 STOVL variant involves similar issues.

There is little doubt in my mind that the Russian seats are remarkable. Very heavy – I believe as much as 2-2.5 times MB seats- but remarkable devices. I can think of 7 airshow saves where other seats might not have hacked it. Anatoly at Paris in 89 being the first. Their seats have been multi mode for a long time and are cleared for high IAS and supersonic use - which has to be where a lot of the weight was needed.

Milt. I know of his case, but that is all. He was a lucky man and I think still the highest IAS MB escape.

It's ironic that F35 will be using a solution so similar (vectored thrust aft and lift fan forrard) to the one the Russians came up with for Forger...

Thread creep again....but

I think we have to recognise that the Forger layout was chosen as a stepping stone to the Freehand primarily to give service experience of the config necessary for a supersonic vertical lander.

They knew it would never compete performance wise with the Harrier but they had their sights set on the future.

The Harrier was a truly subsonic aircraft. The concept of a single engine at the CG was not the best one (to put it mildly) if the engine was a supersonic one and so taking in a modest mass flow but giving it a huge V.

The subsonic Pegasus was perfect to get VSTOL launched with the simplest possible config. It allowed the aircraft to have a good operating site flexibility just because it takes in a huge mass flow and gives it a modest V which is kinder on the airframe when it is washed by the efflux.

The F-35 has the best of both worlds hot and fast at the back (but out of the way of the intakes and airframe) With plenty of cold and slow at the front to block the hot stuff moving forward into the intakes. Which is doubtless why it won…...?

The AES for the Forger was supposedly part of the whole "concept" that Yakovlev "sold" to the Soviet Navy, who weren't keen on the three-engined layout. I had dinner with a senior Soviet TP who'd been banged-out courtesy of this system and had the video to prove it. There is (or was, certainly it was in the example I sat in) a cockpit switch to let you "arm" the system. After the usual Pilots/Heirarchy battles when the jet entered service it eventually became practice to make sure it was armed, as opposed to the making damn sure of the opposite. I'm given to understand that it took a few tragedies for this to become accepted.

As far as I know, Kiev never had a bow ramp and Forgers never did ski-jumps, although they'd STO after a fashion. The STO in the Freestyle (Freehand was the Forger's experimental predecessor) was, or could be, semi-auto - it did the nozzly/LE-power thing at a point in the TO roll when it felt it was ready, based on the accel.

Well spotted - the 141 anyway!

I should be put down really.....

NoHoverStop - you are right, Kiev didnt have a ski jump - what I meant was STO off the ship. They only attempted to do this in the last year or so of the Forger's service, otherwise all landings and takeoffs were strictly vertical.

I read the experiences of a Forger pilot (in International Air Power Review) and he describes in detail the landing procedure - even the simplest landing had a mind numbing number of steps!

The Forger actually had an analog equivalent of a modern digital flight computer, which the pilot had to shift from mode-to-mode manually! No computee no flyee!

They even attempted to use this thing in Afghanistan - limited combat abilities even in the best of circumstances, what made them think they could fly it in the high density attitude of Kabul?
There is a picture of a Forger taking off and shutting down the Kabul airport for days on end due to the dust it raised!

John - its gives me great pleasure to think I was thinking the same thing as you at the very same moment! Ahh - touched by greatness :-)

Soviet/Russian engineering - it works, it's not at all pretty. Or it explodes
Italian engineering - it's pretty, it doesn't work
German engineering - it works perfectly, it costs its weight in platinum
US Engineering - it works except when it doesn't, it's not that pretty but somehow we all end up using it
British engineering - it works, it's pretty, it's cancelled

Steamchicken

I wish I had thought of that.

JF

Staemchicken...
British: Make the best ejection seats in the world and the world uses them. They are even fitted into Chinese a/c now!

Vertical seeking seats were experimented on by the Americans and they did work. However, the high lateral forces produced in the "flip" from inverted to upright would have ripped a human head off!!:ugh:

BOAC,

The unfortunate pilot suffering the uncontrollable roll in the Harrier was Nigel Storah. He ejected into the football pitch at Gutersloh and didn't survive the impact. He was previously a "creamie" QFI at Linton. I recall the event vividly as it occurred just as I drove through the main gate to begin my tour on the station. I had hoped to have a bier or two with him to celebrate our lucky escape from a JP icing incident about 3 years previously.

One horrible wet night in 1978, February 6th according to my logbook, Nigel and I were flying back from Waddington towards Linton. We had transitted to Waddo and unsuccessfully tried to break cloud for night circuits there, due to bad weather at Linton.

Our Mk3A (XN494) got very badly iced up and slowed down more and more until it could eventually only make about 130 knots IAS. As we briefly cleared cloud, against a dulled moon we saw that the wings were covered in thick, rough textured white ice - I distinctly recall thinking the tip tank on the port wing looked like a huge cauliflower. The engine was giving a maximum of 90% rpm, probably not a lot of thrust. The handling became quite waffly and we agreed that if it stalled I would eject immediately on his command and he would follow. We were going through the pre-ejection checklist, checking pins stowed, leg restrainers correctly attached, harness tight and locked etc, when we found a bit of clear air between layers of cloud. The engine gradually picked up to 95% and we made it back for a straight in PAR at Linton. Nigel flew the approach, meanwhile I remember confirming I could find the seat bottom handle at least a couple of times and going through the parachute drill in my mind. We taxied back in and as we stood by the aircraft, in heavy rain, long slabs of melting ice slid off each wing onto the dispersal. To this day I have never been so pleased to be back on the ground.