Originally Posted by
FlightDetent
Midland63 The L/G is kept down during the wind shear escape routine (also) because terrain impact is a possibility. The loads absorbed by the collapsing undercarriage structure make survival of the occupants more likely, any straw counts.
While the doors protruding into the airflow will add drag, and the explanations above that it is accounted for in the EFATO case are sound, the mainstay B737 does not have any on the main landing gear. Go figure? The priority on both GWPS (terrain) and WSHR (loss of lift) scenarios must be to fly the aeroplane up, as the single objective. I gather that history teaches us messing with configuration might be detrimental to the crew's coordinated effort to ensure max thrust is set and peak climb performance is established (with speed-brakes retracted).
My best guess is that avoiding the doors' extra drag applies for GPWS, where the danger of impact is truly immediate. For WSHR, the impact-survival aspect would be the reason, which covers the 737 too. As well you want to keep the procedures simple and similar as much as practicable. What is seen in the video may be better described as a low-level G/A with unavoidable touchdown due to a de-stabilized flare, owing to gust (most likely). The industry standard wind shear model is probably different, though related. Still, the L/G lever is not to be touched!
it was some years ago, but an Airbus Flight Test Pilot, Engineer and performance geek gave a very close answer to the above WRT windshear escape at a getting to grips chat . They stated that in days of old, with older designed airframes, and less powerful engines, raising the gear was performance limiting, in some cases even in benign conditions. These aircraft needed full power for missed approaches , and had little power to reduce for takeoff .
But with modern designed, engine thrust can be reduced by upto 40% for takeoff at lighter weights (A380) and have max landing weights almost 200T lighter than takeoff weights (A380) . For missed approaches reduced thrust is used to limit climb rates. Performance wise, modern design of airframe and engines is far superior to a lot of older designs (not all though) .
As speed when after takeoff or fully configured for landing is low, and for modern Airbus FBW the effect of raising the gear is considered minimal .
However, they consider windshear encountered below 500 feet as the most performance limiting . As on approach speed will be established at Vapp and, with autothrust, Eng RPM may be low, putting the aircraft in a low energy situation. Due to the chance of ground contact, it was decided not to change any procedure, but rather have both pilots fully concentrating on flying the aeroplane without any distraction .