Top of the loop
Why close to zero G. The wings are still flying so G can still be pulled all round the manoevure. I don't know the Hunter stall speed but with 23 degrees flap it's going to be lower than in clean configuration. I would expect it still possible to pull between 1-2g over the top. No need to float it....
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#Deefer
You will also be equally aware that de facto zero energy inverted at <3000' is a poor place to start a recovery from the inverted. Kind of limits the options, would you not agree? You offer the thought I would strongly disagree with the notion that may only have been 10 seconds to sort something out at this point even if he had been concerned about his airspeed, or gate height. This is the fact: it was 12 seconds from inverted to impact. I think a two second margin to allow the eventual brown endorsement to spread evenly seems appropriate. The best option is always to stay out of trouble. Once in trouble, time does fly by. When did Noah build the Ark? BEFORE the storm... My point is that the problems were already in place at the top of climb. Your comment: If the aircraft was close to zero G at the top, the stall speed would also have been close to zero. At the top, assuming the engine was still developing thrust, the aircraft would have started to accelerate in both senses of the word - thrust + vertical component of W increasing the airspeed, and the G acceleration of pulling around the curve. So: You volunteered at the back so step up: you grab the pen: Talk me through the recovery from 100Kt [assume therefore ZeroG] inverted at ~ 2600' agl in an a/c with a 130Kt stall in an a/c with an est 75% fuel load including underwings on a hot [28 degC] day There's the board.... |
Reheat
No such thing as a 130kt stall speed. Stall is an AoA. But I'm sure you knew that. |
I can't claim to know the stall speed of a Hunter with that flap setting, but I bet it's not far away from 100kts....
So he was in a silly place even if he'd been the right way up at 2600' To be inverted, surely worse. To try and pull through from there??????, Braver than me. |
Originally Posted by AtomKraft
(Post 9109267)
I can't claim to know the stall speed of a Hunter with that flap setting, but I bet it's not far away from 100kts....
You are talking about a stall as if it has a related speed. |
I've been away from this thread for a while.
Observations and questions on latest info: 2600ft at the top of a loop, if it is accurate, is way too low. 100kts at the top of a loop is way too slow; and I know stalling is dependent on AoA. The Hunter, in RAF service, did not have an AoA gauge. Did the naval T7/T8 which was used for Bucc checks? I don't really know. Had the civilian operator of this aircraft retro-fitted an AoA gauge? Does anyone know. AoA is crucial at that speed. If he was at 100 kts at the top of the loop, with any aileron input the aircraft would have been exposed to an inverted spin from which there would have been no recovery. AH has a total of 40 hours on the Hunter collected over 4 years. Well, I'm sorry, but IMHO that is nowhere near enough type experience for anyone to be doing this sort of flying. Years ago in the Service, no-one would have been cleared to do solo low-level aerobatic displays at air shows without first amassing several hundred hours on type, if not over a thousand. Attention should perhaps focus on the system which cleared him to do it. |
Wingswinger
2600ft at the top of a loop, if it is accurate, is way too low. The accident flight was recorded by the NATS radar facility at Pease Pottage. The maximum altitude recorded during the final manoeuvre was 2,600 ft amsl (recorded by Heathrow radar), which may not reflect the peak altitude achieved because the radar data was not continuous. |
Originally Posted by Wingswinger
(Post 9109403)
If he was at 100 kts at the top of the loop, with any aileron input the aircraft would have been exposed to an inverted spin from which there would have been no recovery. Years ago in the Service, no-one would have been cleared to do solo low-level aerobatic displays at air shows without first amassing several hundred hours on type, if not over a thousand. . To your second. Whilst I agree to some extent, an in service Hunter display would have been much more aggressive. |
Reheat On,
I have my coffee now, so I'll have another bash at explaining: You will also be equally aware that de facto zero energy inverted at <3000' is a poor place to start a recovery from the inverted. Kind of limits the options, would you not agree? I sense your experience of low level aero's might be a little rusty? Talk me through the recovery from 100Kt [assume therefore ZeroG] inverted at ~ 2600' agl in an a/c with a 130Kt stall in an a/c with an est 75% fuel load including underwings on a hot [28 degC] day May I leave school early today Sir? |
High(ish) speed run-in. Gentle(ish) pull-up. Topping out at 3000 ft(ish) and 100kts(ish)
...that was flown with idle(ish) power. ...i don't know why. i'd love a coffee. but a lot of people in the queue. |
Aerobatics 101: The Loop
1. Have enough speed on entry to get over the top. Low level, have enough speed to complete the loop at some margin above entry altitude with a more aggressive pull past the vertical on the backside of the loop.
2. On entry, don’t pull too gently: you won’t get over the top. Don’t pull too hard: you won’t get over the top (too much g kills speed, see 1). 3. Start relaxing pull as you come to the top of the loop so you float over at less than one g. This makes the loop look round and avoids the risk of a stall. Note that the airspeed gets pretty low. It doesn’t matter if you’re not pulling because stall is a function of angle of attack, not speed. 4. Don’t dilly-dally about beginning the pull on the backside of the loop. The airplane starts accelerating pretty quickly so you don’t want to spend too much time pointed at the ground. 5. Play the pull coming out of the vertical on the way down so as to complete the maneuver at or above the entry altitude (see 1). |
The AAIB special bulletin states that the highest recorded altitude was 2600' but that then radar return was not continuous. This would appear to leave open the question as to whether the aircraft went higher after this reading, or had been higher before it, but thinking about it would that not make the situation worse?
If the aircraft was heading upwards when the 2600' and 100kt were recorded, then it would suggest that it was even slower over whatever the eventual "top" was. If it was on its way down when 2600' and 100kt were recorded, this too would point to it having been slower over whatever the top was. Is this logic too simplistic? |
The Hunter T8B had an AoA system, but I cannot recall whether the T7A did. Photos of WV372 (a T7) shows it not to be so equipped.
Hopefully the cockpit imagery recovered from the aircraft will show whether the JPT limiter was operating correctly; if I recall correctly it becomes active about 30 sec after the nose undercarriage has locked up. If the system fails, it can cause either a high JPT or a significant loss of thrust; however, the JPT controller can be manually isolated in flight by use of a switch near the throttle, although it is a bit of a fumble to find it. I hope that sufficient documentation exists to calculate the normal take-off run of WV372 with an 8 kt tailwind; the AAIB has said that the lengthy take-off run on the day was 'probably' due to the prevailing conditions, but this needs closer inspection, in my view. |
falcon
If the aircraft was heading upwards when the 2600' and 100kt were recorded, |
Wiggy,
Thanks, I think you are correct. Having re-read the bulletin, the height and speed data are indeed from separate sources. |
No doubt the direction of take off will be commented on by AAIB in the final report. For example if the wind benefit is negligible it may be beneficial to land on a runway with an uphill gradient or take off with a downhill gradient.
Another factor to consider is that when using 02 at EGSX you have Stanstead directly ahead (and they may give you a squawk whilst on the ground at EGSX) and when using 20 you have Stapleford ahead. My understand is that for landing the Hunter at EGSX he preferred 20. Note. Last time I commented about runway gradients and choice the mods deleted the post. |
Well BEagle, the take-off and the final manoeuvre certainly appear somewhat slugish. The RR Avon 122 certainly could have power issues. However, I would expect it to show problems in the rpm/tgt relationship, if that were the case.
OAP |
Does anyone know how AH is getting on in hospital? I wish him well and the same goes for his family and friends, it must be a hard time for them. May
GBWY. MB |
I don't recall 372 having AoA guage when I was flying it in 1983.
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Hunter loops
FWIW in a Hunter GA11 (navy single seat) with no tanks and light fuel load with a minimum of 200 feet start finish height it was possible to top out at 1800 around 95 knots and 2 notches without increasing the laundry bill. T8 - would not try that low or slow but still a very capable machine. Fuel and tanks made a big difference in performance obviously.
Great shame Shoreham but I think the investigation will produce the right answers. |
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