Flight TestingA forum for test pilots, flight test engineers, observers, telemetry and instrumentation engineers and anybody else involved in the demanding and complex business of testing aeroplanes, helicopters and equipment.
I was asked a fairly good question recently from one of my non-aviating friends, and it left me stumped for an answer.
He'd been watching the documentary about the testing and certification of the A380, and had noticed all of the test crew wore parachutes. His question was how they would all get out of the aircraft in the event that something went wrong?
I have to admit, it had me stumped. My guess would be that in the absence of a dedicated escape hatch, the crew would be reduced to leaving by one of the main doors (presumably rigged for the test flights so that they can be opened/jettisoned in flight), or through the fuselage in the event of a catastrophic failure.
".....how they would all get out of the aircraft in the event that something went wrong?"
In a less than orderly fashion I would suspect. That said, if the aircraft is in that much peril, I would suspect that any exit that you could fit through would suffice.
That said, other than military aircraft (who would hopefully eject), I don't recall the test crew ever leaving the aircraft, in recent times at least. In fact, quite the opposite has occurred, with less than favorable results in one unfortunate case.
Think there's an error in thinking that the aerodynamic test aircraft has an interior, and thus exits, like a normal airliner. Our RJs have a modifed lower access hatch forward that is hydraulically powered to open against the airflow & act as a blast diverter. The cabin floor opens to provide a smooth slide out. The aft baggage door is also powered such that it can track inboard to provide an aft means of escape. Some smaller biz jets have large sections of the fuselage able to be blown out explosively with, again, a blast door arrangement to get you safely through the boundary layer.
The pressurisation system is also modified to allow full emergency drepress to ambient not to an intermediate cabin altitude plus, of course, gaseous oxygen for all. Any hazardous testing limits the crew (normally to three, two pilots & an FTE).
FYI it's not just test aircraft that have bail out doors - the KC-135 has a similar facility just at the rear of the cockpit.
ICT SLB has nailed it, and hopefully I never get to try any of the posted methods.
Once the aircraft is depressurized we would transfer to our own oxygen supply contained within the parachute pack and exit the aircraft in an orderly fashion! Standard issue USAF helmets and O2 masks are also the norm for this type of flight. The parachute also contains an automatic opening device in the event that we're not able to open it ourselves.
On our next aircraft we're also going to be using a "firemans pole" type of exit through the floor - I believe that the Shuttle is also equipped with something similar.
The Concorde flight test prototype at Duxford has an escape chute (looks a bit like a dustbin with the bottom cut out) in the floor just behind the cockpit. I think that they even tested it with dummies in front of the blower tunnel at either Boscombe or Farnborough - probably Boscombe.
There was a successful full crew Merlin abandonment with personal parachutes out of Yeovil - early/mid 1990s from memory.
Genghis, Should have also stated that we do the anthropomorphic dummy on all our escape hatches (except the explosive ones). Agencies also do the escape drills falling out onto mattresses before they join us on Cert flights.
I once did a cabin layout spiel on a Challenger to some Flight Checkers from Scott AFB. When we got to the Aft baggage bay, which is accessible in flight, they took one look at the door and rejoiced at the prospect of an escape hatch! Guess your view changes when somebody's shooting at you.
The flight test prototype BAC 1-11 G-ASYD at the Brooklands museum also has an escape hatch. This aircraft was fitted with an anti-stall/spin rig and parachute for stall testing carried out in the aftermath of the "deep stall" accident to G-ASHG.
Many civil aircraft have escape hatches fitted utilising the freight door to allow departure from the aircraft.
The original forward escape hatches on the One-Eleven and the VC10 were of a similar design concept. Essentially, a door held in place with explosive bolts replaced the freight door. On firing the bolts, levers on pretensioned torsion bars attached to the inside of the fuselage lowered the leading edge of the door into the airstream, which caused it to fly away. Any residual cabin pressure assisted the operation. There was a large duct, or trunking, fastened flush with the cabin floor and to the freight door surround for the crew to jump through. Within the duct was a spring-loaded blast shield that normally projected above the floor. It dropped down to project into the airflow on jettisoning the freight door. The function of the blast shield was to allow escapers to clear the fuselage and to progressively decelerate them to the speed of the airstream, rather than for the deceleration to be instantaneous. The duct and blast shield were of sheet metal skin, stringer and rib construction. The freight bays were sealed from the cabin, to be representative of production aircraft in this respect, so that associated flight and ground testing could be conducted. The escape drill was to depressurise the cabin before firing the escape hatch.
During the incident on the prototype VC10, G-ARTA, on December 31, 1963 the behaviour of the aircraft was rather alarming so the escape hatch was fired at full cabin differential pressure, around 8 p.s.i., in case the aircraft broke up before the crew could escape. Consequently, the duct in the freight bay and the cabin floor had to instantaneously withstand this differential pressure because the freight bays were not vented. This resulted in the escape chute being crushed and much of it tore out of the aircraft. Moreover, many areas of the cabin floor buckled, including the floor beams, which contained the flying control cable runs.
Following the G-ARTA incident, it was recognised that there could well be circumstances where there would be insufficient time to depressurise the cabin before needing to escape. To overcome these problems, all test One-Elevens with escape facilities, subsequent to G-ASHG, had beefed up escape chutes; i.e. G-ASJA, G-ASJC, G-ASJD and G-ASYD. (G-ASJB was scheduled to undertake performance and crew training, therefore, did not need escape facilities due to the low risk nature of testing, though she did have a rear escape hatch.) Constructing the escape chute and the blast deflector from thick (approx. 1.5”), high density and multi-laminate plywood did this. Moreover, front and rear freight bays were adequately vented to the passenger cabin. Indeed Concorde’s facilities were similar to the modified One-Eleven system.
A lever was added outboard of the co-pilot’s seat which mechanically opened the pressurisation control valve to rapidly depressurise the cabin so the door in the rear pressure bulkhead could be opened to give access to the escape hatch in the rear ventral door.
The BAe146 used the cabin service doors as escape hatches. Each door was specially modified without hinges, and when unlocked a large pneumatic ram was used to push it out. Cabin pressure was dumped beforehand via a ‘dinner-plate’ sized butterfly valve in a nearby cabin window – practice cabin pressure dump was no great event, IIRC it took 20 secs or so. The crew wore self contained parachute / oxygen systems with static line deployment. The rear door was the primary exit, avoiding the hazards of engine, gear, and extended flap, but if necessary, the front door would have been used. The usual ground tests were conducted. The only significant ‘risk’ was the ‘run’ to the back of the aircraft guided only by a rope supported from the roof. Latterly of course, the 146 rear passenger door was converted for para-drops; a pull-in and lift up-and-over mechanism. Initial tests involved sand bags thrown out from 50 ft tower flybys and then the intrepid ‘military’ para-testers from 10,000ft for real. Many demo jumps were conducted in the UK, Europe, US, and Australia; IIRC some involved depressurization and jumps from high altitude – and some visits by people of whom you did not enquire their base or unit.
Later versions of the HS125 used a hatch/hole in the fuselage above the main wheel well. A clip-on static line parachute escape required the gear to be down, hatch up, and then a jump through the hole in the floor. Prior to this design, various forms of a fireman’s pole or pogo stick from the main door were considered, also a pole for each crew member, rotating about the door sill which would have taken the crew out of the main door and below the line of fuselage / gear.
Pal of mine was a flight test engineer on the A380 and he mentioned a big slide down into the hold with a special door- I assume there was a dump valve somewhere. Not sure how it would have opened against the airflow though.
Don't know why one needs a parachute. Once the aircraft starts to spin you will be pinned to the wall. No way you will get out.
Why would it get into a spin in the first place? Most likely scenario (on our aircraft) is a deep stall - aircraft is either on it's back or severly nose up and dropping like a rock. We run grab handles along the ceiling and the floor for exactly that reason.