Front Office Politics

First published 15 September 2005.

In the aviation world, the cockpit is often referred to as “the front office”.  And just like any ordinary ground-based office, if it is to function well, the people in it need to communicate effectively, with unity of purpose and effort.  In the case of Air France 358, it appears that the captain and co-pilot may have had a relatively minor but hugely consequential disagreement during their landing rollout.

Montréal radio station CJAD (AM 800) cites an interesting story in Paris daily Le Figaro, “Crash de Toronto: les mystères du cockpit” (poor BabelFish translation to English here).  The French newspaper reports it has somehow obtained details of the Air France 358 crash, gleaned from the plane’s FDR (flight data recorder).  The crash was previously discussed here in posts “Good Landing?” and “How Long Is Too Long?”  The FDR, incidentally, remains in the custody of Canadian officials and they do not expect to publicise the data, along with the CVR (cockpit voice recorder) transcript, until October 4th.

According to Le Figaro, the FDR shows that twelve seconds elapsed between AF358’s touchdown and the application of reverse thrust.  Normally, reverse thrust is manually engaged by the pilot seconds after an aircraft touches down.  The onboard computers have a series of interlocks comparing variables like compression of the main gear struts, wheel rotation speed, throttle setting and radio altitude.  When all of these requirements are met, the computer will allow the pilot to move the throttles into the reverse thrust setting.  The twelve-second delay is not in itself damning, because thrust reversers do not contribute that much deceleration; the main gear brakes contribute the most to slowing a landing aircraft.  If you look at the landing distance modifiers chart below, you can see the effect that the reversers have under various landing conditions.

Figure 1. Corrections to Actual Landing Distance

A340_Landing Distance_Corrections

(click to view larger image)

On dry runways, thrust reversers contribute the least amount of braking power (-3% landing distance), because the landing gear wheels have maximal traction and grip on the runway.  As runway conditions change and become wet, the wheels have less traction, and reversers contribute more to the deceleration of the aircraft (-7 to -10% landing distance).  Under icy conditions, of course, the wheels have very little traction and reversers contribute greatly to aircraft braking (-28% landing distance).

Reviewing our earlier data, we know that Air France 358 touched down on Runway 24L with 5,000ft remaining of the 9,000ft landing distance available.  AF358 decelerated from its touchdown speed of 148kts to 120kts, and in that time it travelled 2,296ft (700m) without maximum braking (thrust reversers, spoilers and main gear braking), but the FDR shows it did at least use the main gear brakes.  As Le Figaro points out, loss of twelve seconds and 700m (2,297ft) on a normal 3,000m (9,843ft) runway is not a big deal under normal (dry) conditions, but that changes when heavy rainfall enters the equation.  Wheels have less traction, and therefore brakes have less effectiveness.  Can the thrust reversers, spoilers and main gear brakes take an A340-300 from 120kts to 0 in 2,703ft on a wet runway?  AF358 was travelling at about 80kts (150km/h) when it ran off the end of Rwy 24L, so apparently the answer is “no”.  [But if you throw in another 656ft (200m) and a heavily wooded ravine, the answer is a qualified “yes”.]

What might cause that twelve-second delay?  The article says it could be attributable to the pilot (PNF, handling radio communications and FMS) and copilot (PF, landing the aircraft) disagreeing over the proper course of action.  The reporter doesn’t say whether this is the case, because the CVR (cockpit voice recorder) transcript has not been released.  But I will bet anyone right now that the delay was caused by the aircrew disagreeing over whether to apply takeoff thrust and go around, or apply maximum braking and commit to a full stop landing.  That is the sort of decision that needs to be made and executed very quickly and very early in the landing roll, otherwise you will find yourself in a position of having too little runway to safely do either.  And that’s when things end badly.

Remember how I talked about crew resource management in this post?  Good CRM is critical to good flight operations.  If one of the flight crew detects something amiss, but doesn’t mention it forcefully enough, or is ignored or overruled by the other pilot, things can go wrong.  It is important that both the PF (pilot flying) and PNF (pilot not flying) respect each others’ judgment, and that one unambiguously submit to the authority of the other, even if opinions differ on the proper course of action.  Reaching a balance between opinions of two highly-trained, highly experienced pilots, and doing it in a moment’s notice, is tricky work under the best of circumstances.

Some other interesting tidbits from the Figaro article:

  • I asked in my original post whether it might have been better to use the adjacent longer (9,697ft) Rwy 24R under low-vis conditions, instead of the shorter (9,000ft) Rwy 24L that AF358 used.  According to Le Figaro, Rwy 24R’s ILS (instrument landing system) had been disabled by lightning on the day of the accident.  Air France regulations quite sensibly require the aircrew to use ILS guidance under marginal weather conditions, so 24R was not an option.
  • Pearson Tower communicated weather conditions of moderate winds (11kts) to AF358, but the A340’s black box indicates 23kt winds to touchdown.  Apparently Pearson’s anemometer and windshear detector were also inoperative that afternoon.  No word on whether the Arrivals or Tower controllers were aware of the weather detection problems.
  • The captain’s seat failed (“ruptured” is the word they use) at some point during the crash, and he sustained spinal injuries.  Only three years from retirement, he will probably not fly any more.  The copilot will resume flying at the end of this month, after a routine simulator checkride.

Another problem is that Pearson does not have distance-to-go markers on its runways.  These are indicators that tell a pilot how many feet of runway remain in front of him.  These markers are standard on U.S. and Canadian military airfields, and many of the United States’ large civil airports, but they are not present at high-traffic civil airports in Canada.

Overall it’s not a pretty picture, if all of these unsourced assertions are true.  An airport (and air traffic control) whose weather detection capabilities were impaired, and may not have known about it.  A key runway unusable because its ILS equipment was disabled.  The busiest airport in Canada, without appropriate flight safety markings on its runways.  An experienced aircrew that failed, at one of the most critical moments of flight, to commit to a go-around or full stop.

I think one can call this as “pilot error” under the circumstances, but note that there were a lot of mitigating factors.  Perhaps ATC should have been more circumspect in routing and traffic flow, in light of 24R’s incapacity.  Certainly the absence of reliable wind indications and windshear detection should have forced AF358 to an alternate, assuming that ATC was even aware of the problem.  The go/no-go decision should absolutely have been made prior to touchdown — AF358 had already floated down 40% of the runway before the wheels made contact.  If Pearson had distance-to-go markers on its runways, the Air France aircrew would know whether they had enough room to go around or fully stop.  They, in turn, would have less cause for disagreement because numbers would be right there in front of their windshield.  Delaying a critical decision for twelve seconds in the rollout might have cost people their lives.  We are all are extremely lucky that no one was killed, given the circumstances.

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One Response
  1. Air France 358 crash was avoidable

    First published 03 October 2005. But lazy, half-assed reporting was not. Sunday’s Toronto Star had a nice three-page story about the September 2nd incident involving Air France 358 (web version here). As citizens of this city are no doubt aware,