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Robert Atkinson 201/12/2019 20:49:01
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406 forum posts
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We used to hear the tail end of Concords supersonic runs up the bay of Biscay all the way in Christchurch on cool quiet evenings.
And I did of course hear the booms from Thrust SSC back in 1997. The car went supersonic 5 times. One of these was unintentional. The car was to run to a predetermined indicated airspeed which should hav been just below Mach 1, There was however a clear boom. The first suspect was the airspeed indicator calibration (which was my responsibility, I built the speedometer and Mach meter for the car) but it turned out that when calculating the target speed they forgot to allow for the affect of altitude on Mach number. The Black Rock desert is at about 3900ft above sea level.

Robert G8RPI.

Meunier01/12/2019 21:19:24
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I had to check to see that Martin C did not correspond with Martin Baker

DaveD

and we occasionally get sonic bangs when the boys in blue from Mont-de-Marsan base get it just that bit wrong on low-level sorties..
with many buildings around here roofed with Roman tiles, they do rattle a bit !

Martin Connelly01/12/2019 21:26:27
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I was near an RAF runway when the crew banged out of an F4 as it was landing, I was at Wideawake airfield when an F4 did a flight test after an engine change. We knew there was going to be a sonic bang.

Martin C

Mike Poole01/12/2019 22:09:10
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Living next to Martin Bakers test facility at Chalgrove we hear quite a lot of test ejections from the Meteors they use for testing, I have not felt that they sounded like a sonic boom but I lived a few hundred meters from the ejection point the sonic booms were rather more distant and the culprits were possibly from the Clutch stations of Wildenrath, Brüggen, Gutersloh etc. Or maybe the Luftwaffe with their widowmaker Starfighters, who knows it was a long time ago.

Mike

martin perman01/12/2019 22:50:52
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1689 forum posts
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A slight aside, I was sent to Martin Baker's site on the Isle of Man to service some machine tools many moons ago, I had never been before and when I walked out of the Airport building I got into a cab and said the Martin Baker Factory please, he drove 50yds and did a 180 deg turn and 50 yds again on the other side of the carriageway stopped and said there you are sir no charge. Silly me.

Martin P

Neil Wyatt01/12/2019 23:52:08
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Heard my first sonic booms when Concorde first started - it used to go supersonic over the Bristol Channel, I was most disappointed when then made it wait until it was over open sea.

Short Skyvan was among my favourite Airfix kits.

Neil

Robert Atkinson 202/12/2019 19:28:52
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406 forum posts
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Thrust SSC had a Martin Baker ejection seat rocket motor mounted "upside" down in the nose. The intention was that if the nose started to lift it would fire keeping it on the ground long enough for the hydraulic ride height control to jack the rear end up and generate aerodynamic downforce and drag. The test firing was pretty impressivebut diddn't sound like a sonic boom. The main seat "gun" cartridges might sound a bit like it though. I've worked on a Skyvan (a 3A) and several 330's and 360's It's no coincidence that Shorts were asked to build the Miles Aerovan a couple of years before staring work on the Skyvan. It's was more a case of what not to do rather than copying it.

Robert G8RPI.

Martin Connelly03/12/2019 21:50:48
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On the F4 as well as the initial main gun cartridge there is a second cartridge that is triggered after the seat has travelled half way out of the cockpit. The idea was to keep g forces below a dangerous level by not putting out the full force needed for ejection in one go.These two cartridges put enough pressure into the seat tube to push the seat and crew member out of the cockpit at a high G force so is not just a few psi. Once the seat has risen far enough the tube that is part of the aircraft and the seat part company and this pressure is released with a sound like a piece of artillery being fired. If you look at pictures of aircraft where the seat has been used you can see the tube protruding from the cockpit. The rocket only fired after the seat had left the cockpit.

Martin C

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