ATSB Sends Garuda Recorders To Manufacturer

Air Safety Week, March 19, 2007

What if they'd flown through a sharp gust or thermal and picked up a temporary tailwind and just lowered the nose to correct the overshoot trend? Well, that would just indicate a fairly inept handling of a common everyday problem. But unless there was some system failure, put it down to an inability to cope with the environmentals -- and perhaps the relative inexperience of the RH seater.

The captain was quite experienced, but possibly inattentive and just let it all go too far. Porpoising is a PIO, and by definition it can be a self- sustaining destructive process. Pilots aren't taught about porpoising in any syllabus, don't know the "escape", and so their first encounter with it will be an eye-opener. Task fixation (leading to task saturation) is by far the most common cause of mishandling accidents during the landing evolution. For some examples of porpoising, try tinyurl.com/33ektj.

From what is known to date, it is suspected that the first officer, flying the visual approach, allowed the aircraft to get too high on glideslope. Without flap, but not realizing it initially, and already using speedbrakes to get down, he likely flared high and then touched down hard about 685m's into the 2200m runway. After bouncing again at the 885m mark and then losing the nosewheels on their third hit, it appears he latterly attempted to go round, but was thwarted by the other pilot simultaneously attempting manual wheel-braking.

The buffeting on finals (remarked upon by the Australian journalist onboard, Alessandro Bertellotti) is a known characteristic and could have been caused by a non-recommended use of speedbrakes with 30 degrees of flap, in an attempt to burn off the excess height. However, at a higher speed, speedbrake without flap could also have caused the buffeting noted by the passengers.

Elevator effectiveness in the flare is reputedly affected by speedbrake extension at any flap deflection. Speedbrakes are usually stowed by no later than 500ft AGL (at which height the approach should be stabilized or a go-round commenced). However, that journalist flies about 100 times a year. He is a credible witness and is reasonably sure that the trailing-edge flaps weren't deployed, at least not as he'd been used to seeing them.

Additionally, he was quite certain that the speedbrakes were up throughout. Those double-slotted trailing edge flaps are quite unmistakable when extended, so that witness's input tends to confirm that the flaps were "locked out" at only a few degrees of deflection -- i.e., that the aircraft was flapless and thus prone to floating along for a delayed touchdown.

Note that the no-flap approach visual attitude and the normal approach attitude and flare for touchdown are chalk and cheese. Raising the nose to the normal flare attitude while both hot and flapless, but with speedbrakes, would have led to the next complication.

Per standard operating procedure, the auto-throttle (A/T) should be cancelled no lower than 100ft AGL, but we're suggesting that it wasn't; that this step also was forgotten due to the pace of events. After flaring too high (possibly because of the speedbrake and being a natural tendency because of the ground-rush impression at the higher speed) and with auto-throttle still selected, the auto-throttle's thrust increase would have kicked in at any height above 27ft RA (radar altimeter).