Talk:Air Transat Flight 236
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[edit] Fly-by-wire has nothing to do with it
I took the liberty to correct the sentence which stated that the Airbus aircraft was fully fly-by-wire, hence it could not be flown without the engines unless it could rely on the ram air turbine. This statement was misleading, as the most important effect of losing both engines is not the loss of electrical power (there are backup power sources - batteries, or even the APU when there is some fuel left), but the loss of hydraulic power. All modern 100+ passenger aircraft have hydraulicaly powered flight controls, therefore cannot be flown manually when all hydraulic power is lost. Hence the need for a ram air turbine, to provide limited hydraulic pressure and ensure some (although reduced, and all the more reduced as the aircraft flies slowly) controllability.
Mandarine--81.56.83.86 19:20, 4 October 2005 (UTC)
- I've taken the liberty of reverting your change, pending you supplying a source. The National Geographic program portrayed the issue in terms of the electrically-powered flight control systems and fly-by-wire was a significant differentiating factor when the first Airbus was built, and continues to be so to a lesser degree today. The way you worded it is to ignore the issue of fly-by-wire and its total dependence on electrical power completely. --Icd 00:06, 27 December 2005 (UTC)
22:59, 20 September 2006 (UTC) Mandarine's revised text is very accurate and preferable to the previous/current. Take care with terminology. "Fly-by-Wire" refers to the electrical command of systems and is low in power consumption, (being based on 28V DC for the A330). For the A330, it is coupled with hydraulics to provide the "muscle" or "power assistance". Large modern aircraft are too large for pilot input to be transferred direct to the control surfaces, hence the need for assistance.
Mechanical command,no assistance required. Mechanical command, hydraulic assist Electrical command, hydraulic assist Electrical command, electrical assist.
Since the electrical command system is a (relatively) low power consumer, in emergency it can be powered by dedicated batteries, thus no reliance on engines or fuel. Regarding the comment about "loss of landing gear brakes", I consider this mis-leading. An hydraulic accumulator dedicated to the brake system, is sized to perform a complete braking action (and is sized to consider the normal leakage of pressure during the period of flight) - this device also provides the pressure to maintain the "handbrake" function, when the aircraft is parked up and without generated power. In this particular incident, wheel brakes made no difference, upon landing. The landing energy was great enough to cause multiple tire burst. With the tire rubber loose on the wheel rim, braking was useless. The photographic evidence clearly show a Circular Segment ground off of one of the main wheels and the tire was utterly destroyed. (I have around a dozen high quality digital photos taken shortly after the landing). (The high landing energy was due to vertical descent velocity, which was also related to forward velocity. Remembering that the pilot had only limited control of the aircraft, the RAT powered only the primary flight controls, so no high-lift surfaces could be deployed. With a single opportunity to land, there was no option for a go-around. Higher forward speed was the pilot's only option for maintaining lift, i.e. controlling vertical descent rate. It can be concluded that the pilot achieved a satisfactory balance between horizontal and vertical speeds,given that the runway was a finite length!)
For the Air Transat aircraft, from the time when it ran out of fuel, the pilot faced the same challenges as for the Gimli Glider, namely no means of assisting the commands. Note: RATs can power either an hydraulic generator or electrical generator, depending on the needs of the aircraft. Whilst many of the current generation commercial aircraft have 3 different hydraulic circuits, new generation a/c have 2 plus an electrical circuit; thus when primary hydraulic power is lost, electrical power is used to control the primary and secondary flight surfaces.
A very early example of the use of current technologies can be found in the late 1940's Bristol Brabazon : http://en.wikipedia.org/wiki/Bristol_Brabazon
[User: Aero-Eng] Aero-Eng 22:59, 20 September 2006 (UTC)
From Wikipedia's own ram air turbine article: "A ram air turbine (RAT) is a small propeller and connected generator used as an emergency power source for aircraft. In case of the loss of both primary and auxiliary power sources the RAT will power vital systems (flight controls, linked hydraulics and also flight-critical instrumentation)." [emphasis mine] The issue as far as control goes is not loss of electrical power; it's loss of hydraulic pressure. Even on a fly by wire aircraft, the actual movements of the controls are caused by hydraulics; it's only the commands that are electrical (a notable exception is the A380, which has a backup electrical control system). Without the feeds from the engines, you need something to generate hydraulic pressure, and that's what the RAT does. -Scott Wilson 01:00, 27 December 2005 (UTC)
- How does the situation the Air Transat flight found itself in compare to an older non fly-by-wire aircraft, e.g. a Boeng 707 which has hydraulic assistance but mechanically linked flight controls? In a no-engine situation, do the controls become completely inoperative, or just very difficult to move? --Icd 00:20, 28 December 2005 (UTC)
[edit] Dirk Dejager v. Dick Dejager
I changed the First Officers name from "Dick Dejager" to "Dirk Dejager" but was reverted. I have seen (and enjoyed) the National Geographic documentary on this and the name was definitely "Dirk". For some written references which use "Dirk", I can mention
Now, I did notice that Air Transat referred to him as "Dick"
Very odd. Sjakkalle (Check!) 08:16, 25 January 2006 (UTC)
Also, a Google Check turns up more on "Dirk Dejager" than "Dick Dejager", and remember that several of the "Dick Dejager" hits are Wikipedia mirrors. Sjakkalle (Check!) 08:18, 25 January 2006 (UTC)
Ah, good. Glad to see some sources being brought to the table. A Google search for "Air Transat Flight 236" bring up Dick several times in the top levels, including a CBC news report, confusingly giving a different name to the link you posted. What I presume is happening is that Dejager uses Dick as a diminutive of Dirk (or possibly vice-versa). I think both should probably be noted in the article (i.e. 'First officer Dirk or Dick Dejager') to prevent this issue from coming up again unless someone has a definitive answer. --Scott Wilson 11:02, 25 January 2006 (UTC)
Thanks, I have done as you suggested and added both names to the article. Sjakkalle (Check!) 12:54, 25 January 2006 (UTC)
