Air India 171 Boeing 787 crash questions
Friends have been asking my opinion regarding the recent Boeing 787 crash in India. Based on the fact that the 787’s gear wasn’t retracting or retracted, the most common speculation right now seems to be that the flight crew mistakenly retracted flaps rather than gear at the “positive rate” point just above the runway.
I’m not typed in the B787 so I can’t say for sure how far apart flaps retraction and rotation speed are. In the CRJ, the following are true:
- the plane won’t take off without some flaps down (i.e., even with full power from two engines it will just go off the end of a 15,000′ runway)
- rotation speed (Vr) and flaps retraction speed (V2+10) are reasonably close, separated by perhaps 15 seconds (admittedly that’s with gear coming up); see “Everything about V Speeds Explained”
- flaps on an airliner move rather slowly
- with two engines at full power, the plane will climb reasonably well even if the configuration isn’t perfect
- given a long runway, less than full power is typically used for takeoff so as to reduce wear on the engines and stretch out the time to overhaul
So… I have no idea what caused this tragedy, but I don’t think that “proper configuration; proper rotation speed; full power; flaps instead of gear just after takeoff” explains a failure to climb. Gear adds drag, but the plane needs to be able to fly in a clean configuration on just one engine and, therefore, with double the power it can easily overpower the gear drag. An inadvertent flap retraction also shouldn’t have caused a crash because, once off the ground, the plane accelerates very quickly toward and beyond V2. The Ahmedabad airport is at sea level and has an 11,500′ runway, which might enable reduced thrust to be used even given the reported 43C temperature. On the other hand, pilots who are sinking would likely push the thrust levers full forward as a reflex.
An obvious explanation is that the aircraft lost power in both engines shortly after takeoff, but it is difficult to think of a way that two turbine engines can fail at the same time. It happened to a Boeing 777 landing at Heathrow due to high altitude icing, but that’s impossible during a hot summer takeoff. It happened to Airbus single-pilot hero Captain Sully (Jeff Skiles nowhere to be found in the media!).
Maybe the fuel was contaminated, but jet engines will burn almost anything and why didn’t the engines quit during taxi?
Separately, should “British man” Vishwash Kumar Ramesh (Guardian) spend all of his future earnings on lottery tickets?
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