Eddie sez:

You could say this hard landing resulting in substantial aircraft damage was caused by the fact the pilots positioned an automatic anti-ice system from AUTO to ALL a little early. You could. But it was really caused by the fact the pilots didn't understand the relationship of the anti-ice system and their fly-by-wire system, and they ran a few checklists from memory, missing the steps that would have prevented all this.
Photo: Embraer EMB-550 Ice and Rain Protection Areas, BEA, Figure 1
Click photo for a larger image
We used to say "an airplane is an airplane, they all basically fly alike." How wrong that is. If you are flying a fly-by-wire aircraft, you should understand that you aren't flying the airplane at all. You are managing a series of computers to fly the airplane for you. If you don't understand the rules those computers are using, you can find yourself in a situation where the airplane is doing something you don't understand.
I am as guilty as many pilots are of thinking that I understand something fully, and being tempted to execute corrective procedures without reference to checklists. Let's say you have an automatic anti-ice system that puts on wing and engine cowl anti-ice systems automatically. Now let's say that system isn't working. No big deal, you've operated for years without such a system. In this particular case, the aircraft's flight control computer wants an extra 30 knots of speed before deciding it has had enough and takes control from you. Following the checklist would have told you that.
We often think that any problems on short final are best handled on the ground, so land the airplane. But as the case of Gulfstream G550 N535GA demonstrates, we may not fully understand the problem. In that case and this one, a simple "Go Around" commanded by the first officer could have snapped the captain back into the game. In this case, the first officer reminded the captain to stay out of the red band on the airspeed tape. This particular aircraft also had a yellow band. So does mine. Turbulence and gusts will push the yellow band up now and then. The red band on the airspeed tape is bad news in any airplane. In a fly-by-wire system it is even worse because it means the electrons may soon be in control of your jet, and you might not like what they do with that control.
This case study provides lessons we all need to take to heart, especially those of us flying fly-by-wire aircraft.
Everything here is from the references shown below, with a few comments in an alternate color.
2021-04-01
2021-04-01
[BEA2017-0674 pp. 1-2]
[BEA2017-0674 p. 2]
It appears the captain did not have a lot of flight experience and only a year in transport category jets. I've flown the L-39 once and remember it as a docile, easy to fly trainer. One huge difference between these nimble trainers and heavier aircraft is inertia. The trainer has surplus thrust to get you out of trouble. The larger aircraft? Less so.
The first officer, while newer to this particular aircraft, had much more relevant flying experience.
[BEA2017-0674 pp. 3-4]
This setup will look familiar to many Gulfstream pilots, but actually simpler. We never turn on the wing anti-ice without the engine cowl anti-ice system, so this does the same thing with a single switch.
[BEA2017-0674 pp. 4-7]
Photo: Embraer EMB-550 Speed Tape, BEA, Figure 4
Click photo for a larger image
Photo: Embraer EMB-550 PFD when AOA protection active, BEA, Figure 5
Click photo for a larger image
[BEA2017-0674 p. 8] The captain said that there had been light freezing drizzle during the night. A thin film of ice covered the RA-02788. Before start-up, the aeroplane had been de-iced using a lorry. The captain started up with the first officer. During the start-up, they positioned the selector on the ice protection control panel to ALL. A failure warning was then triggered. They changed the position of the selector to AUTO which made the message disappear. According to him, the message had appeared because the aeroplane had remained at a standstill and they had not started taxiing.
[BEA2017-0674 p. 8] FDR data shows that in reality the A-I WINGSTAB FAIL message was still present.
The pilots positioned the anti-ice system to ALL "during" engine start which tells me they probably did this before, but certainly not after. That was against procedure because it forced the system on without available bleed pressure and is the reason they got the WINGSTAB FAIL message.
[BEA2017-0674 pp. 10-11]
There is a checklist procedure to fix all this and it requires the system be returned to AUTO first. I think the crew simply reset the system by deselecting/reselecting the ICE PROT WINGSTAB button (as the checklist calls for) with the system still in ALL (against checklist procedure).
[BEA2017-0674 p. 12]
The crew elected to takeoff with the error still uncorrected and neglected the next checklist in the sequence.
[BEA2017-0674 pp. 12-13]
[BEA2017-0674 p. 15]
. . . and other Case Studies
Investigation Report, Accident to the Embraer EMB-550 Legacy 500 registered RA-02788 on 27 November 2017, Bureau d'Enquètes ed d' Analyses pour la sécurité de l'aviaiton civile (BEA), BEA2017-0674
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