737 T/R Logic
Forgive me for a poor memory, but maybe 35 years ago, I recall an accident somewhere in the U.S. where a 737-200 ran off the end of the runway on landing. Can’t remember who/where. But, I do remember it was the typical unstable approach to a wet runway...can’t remember if there was a slight tailwind involved...not sure.
Anyway, typical deal...touched down fast, beyond the touchdown zone, very smooth touchdown. No wheel spin-up, not enough weight to compress the struts, therefore no auto speed brake deployment. Unable to deploy thrust reverse because of all this. Aircraft smoothly glided off the end.
As a result, Boeing incorporated into the logic a Radio Altimeter switch function that would allow T/R deployment below a specified altitude...like maybe ten or fifteen feet RA. (Don’t remember details.) Logic opened isolation valve, or whatever it was called, so hydraulic pressure was available to the selector valves.
Again, this accident occurred on the 737-200 (I’m guessing it was the advanced model...don’t know.), and I don’t know when, at what point, the 737 serial numbers had this feature. But, it was well before the NG.
Maybe someone in this forum has a better memory than I, or can research this.
Fly Safe,
PantLoad