Delta A330-300 Lands Short in Amsterdam

[safetypee]

BraceBrace, I wonder if you are overlooking the aircraft 'flight deck -- main wheel' geometry at TCH. This is of increasing importance in long-body aircraft.

Using the diagram reference at #50:
https://www.airbus.com/sites/g/files...ation-v5.0.pdf

When the flight deck is over the threshold TCH on rwy 22, the wheels are still over the grass, at the calculated wheel over-surface height.
As the aircraft continues on a descending the flight path, the wheel over-surface height decreases proportionately, thus the wheel height over the threshold will be less than the value calculated when the flight-deck was over threshold; thus there is reduced margin for normal flight deviations.

Also (seeking expert A330 input on thus), if the A330 command to retard thrust depends on rad alt, then this too happens over the grass; thence the thrust could be at idle at the point where the wheels are over the threshold (rwy 22).

A late change in the flight path increasing the descent rate, would reduce the already small wheel-threshold clearance with risk of wheels touching the grass and runway lip contact.
This scenario is specific to rwy 22 due to the reduced PAPI to threshold distance - lower TCH, and no hard standing before the threshold; this combination does not apply to all of the other runways.
In addition, and accepting the visual nature of the operation at this point, the action of flaring the aircraft could further reduced height margin.

Specific expert A330 input required:-
During the flare the aircraft pitches nose up, rotating about the cg. The main wheels behind the cg will be displaced downward relative to the cg (the flight path). In long-body aircraft this contributes further height reduction, which in combination with issues above, could be critical.
The effect could also depend on aircraft type and control system mechanisation. Is the A330 flare control law biased towards pitch rate opposed flight path control ?

See marked up diagram, grass is 'green'.

[FlightDetent]

I have argued long and wide repeatedly that PAPIs are not to be used for picking the aiming point at landing. Nor the so called aiming point markers.

While both feel like a one-size fit-all solution and judging by the typical result work fairly well, there are ample configurations where following that guidance will just take the plane into a wrong place.

​​​​​​What happened here was a geometrical necessity, no further research beyond safetypees post needed.

The question still stands the same, are pilots actually trained where to land, have you been? Last time around the agreed answer was 'there's no reason why we should care, know the best already'.

Amsterdam, Burbank...

If somebody links the LAX THR graphic posted on the Skiathos thread, all is revealed. That is built pilot proof for T7/330. Other places might not be.

[Chiefttp]

As far as Boeing procedures, on the 767 My companies procedure regarding high wind conditions with the autothrottles On or Off is to add half the steady state headwind component, and ALL of the gust (above the steady state HW component)to VRef. So if the winds are 120 at 14K gusting to 20k and we are landing on Rwy12. we add 7 knots (1/2 the steady wind of 14k) to VRef, and then all of the gust, which in this example is 6 knots above the 14k steady wind. So Our final additive is VRef plus 7 Knots plus 6knots (gusts) for a total of VRef +13k. As we fly the approach we are supposed to reduce our speed so as to land without the gust increment, but maintain the steady state additive until touchdown. So in my example we should land at VRef +7k. Boeing used to say that this additive was unnecessary if the autothrottles were active, and the additives were only required if the autothrottles were inop, but about 5 years ago (at my airline) we changed the procedure to always add the steady state headwind and gust additive.

[Capn Bloggs]

Originally Posted by Flight Detent

there are ample configurations where following that guidance will just take the plane into a wrong place.

If they are knowingly misleading, then they shouldn't be used. Why do you think that at the vast majority of long-body runways, the PAPIs are around the 62ft/360m in? Because flying a stabilised approach ie not doing a wiffodil under 200ft to extend the approach into the TDZ with the PAPI at the traditional "short-jet" 50ft/290m is too hairy, with not enough room for error (as, I predict, occurred with this A330). The whole point of a stabilised approach is you fly consistently to the flare point, not go off the PAPI above 200ft to stretch the flight to the TDZ. If you have to do that, such as in this case, then if we're going to apply today's cotton-wool level of expected safety, the aircraft shouldn't be using that runway.

At the very least, there should be written, in the company route info manual, a note of the danger of using 22 with it's low MEHt (not that anybody "knows" that yet because the published MEHt is wrong (IMO)). Keep an eye on the AIP for EHAM 22; I reckon there's a good chance it will be quietly republished down to 48ft as a result of this incident.

At KLAX, all the PAPIs are between 390m/67ft and 450m/77ft. EHAM 22, by my calculation, is 287m/49ft. Additionally, all the LAX runways have significant concrete under-runs.

[RatherBeFlying]

Location of the radalt antenna will also have a role in determining wheel height over the ground. Location by the main gear will give a result that is less dependent on body angle than location nearer the cockpit.

I do not know whether or how A has programmed radalt antenna location and body angle into their various laws.

[BraceBrace]

Originally Posted by Capn Bloggs

then they shouldn't be used.

EXACTLY. But they are not misleading, you are expecting too much precision from the system.

The PAPI is a (1) VISUAL and (2) APPROACH aid. By the time you are over the fence, you should already be looking elsewhere and get a complete picture of the runway. You should be looking at touchdown zone markings and lights to get a complete picture. If you are on the PAPI you will be fine, the system will not make you crash. It's not a precision approach category, neither a visual flare aid, we’re not doing carrier landings here, it’s not that type of ”precision”. A PAPI is designed to put the aircaft on ie 3° glide 5NM out VISUALLY (using no GS or path indications on your instruments) and bring you close to the fence safely. Nothing more.

Capn Bloggs, everybody understands your ideas about main gear position on long body aircraft. But you make it sound like this simple light system is an automated landing system giving you sufficient protection all the way down to the runway. It’s not.

PS; it's a visual approach tool so legally, if you are cleared for an ILS... you're not even supposed to look at the PAPI, you visually transition from the glideslope indications to the set of runway lights (nothing stops you from using the PAPI, but it's your responsability).