If you're fast, you may move those numbers up to compensate for the excess energy. With slatted airplanes that slow down quickly when thrust is removed, you want to leave the thrust on late, down to 20-30 ft, or if you remove it higher, you feather it off gradually, making sure you're at IDLE by 20 ft. The other consideration, at the other end of the landing flare phase, is how you handle the thrust reduction, which is a function of the airplane's characteristics and the actual energy state, your speed relative to Vref. I know of a CRJ200 where this happened and it came down hard enough to collapse one of the main gears. All of a sudden you are 20 ft in the air, both IDLE and WOW are satisfied (because WOW isn't immediately removed when the wheels left the ground), and the lift dumpers come out while still in the air. As you do so, in your surprise you may yank the thrust to idle. If you touch down with power on, you'll have WOW satisfied, but not IDLE. WOW = yes when the wheels are on the ground is typically maintained in the lift dumper logic for some seconds even if the signal is lost, to prevent the plane from ballooning back in the air if the gear rebounds enough to lose the proximity sensor squat signals. You must have the thrust at idle at touchdown, because TLA, trust lever angle, is normally one of the arming conditions for the lift dumpers, with Weight on wheels, WOW, being another arming condition. Generally you go by the SOP created by the manufacturer, that was developed in flight test and was briefed in training. If the plane has large double slotted flaps and leading edge slats, the plane decelerates quite rapidly with no thrust on, and hard landings result if this isn't managed carefully. Depends on the airplane and how draggy it is in the landing configuration.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |