FPV and FPV Cage

[Chris Scott]

Quote from Denti:
On our 737 classics it sometimes had 1 or 2 kts difference after a 12 hour day, on our NGs not anymore, no matter how long the flight.

It was careless of me to assume that all pilot’s displays would use raw IRS data for GS, as does the A320 (unless things have changed recently). It may be that the B737NG is using GPS for the pilots’ displays of GS? Let’s stick with the readings quickly available on your IRS MCDU (or whatever it might be called on Boeings − the last Boeing I flew was the 707, with retrofitted dual-INS).

OK465,
Thanks for some more fascinating stuff about Alaska Airlines’s pioneering Cat 3A work, but you are still side-stepping the issue of the (non)-suitability of raw IRS data for FPA displays.
Whether this is displayed by HUD or EFIS (Air Inter A320s were fitted with HUD in 1988), is irrelevant to the inertial/baro argument. British Airways was one of the pioneers of continuous-descent non-precision approaches (SOP since the 1980s) and, when they obtained the A320 (courtesy of BCAL), the FPA made them that much easier and more reliable. The FPA FD function enabled us to fly them to MDA with AP, although many of us preferred to hand-fly using the raw-data bird. (Just for the record, we never level-off at the MDA.)

The fact that there is room for argument about how these relatively simple systems are organised on different aircraft types shows how poor is the documentation supplied by the manufacturers to pilots, and even engineers like NSEU.

Chris