Autopilot level-off at MDA
 

If you are doing the traditional "Dive and Drive" method on a non-precision approach with the Autopilot Coupled, i.e. VS Mode, does any plane/company require an additive to the MDA due to the tolerances of the Autopilot capture/hold capabilities?

I don't believe I saw any used due to autopilot limitations (737, 757/767, A320, MD-11), 3 airlines. If you could enter the exact MDA into the automation, that's what you used.

Altimeter error, along with nav instrument errors are all part of the Flight Technical Error Budget, just set the MDA and go for it.


Gf

Thanks for perspective.

I wouldn't think that you would have to, but I ran into a "technique" (not sure that it is driven by any credible technical data) for specific plane that has that.

Hope more chime in to see if anyone at all does it.

Most operators “round up” to the next 100ft increment.

Every glass airplane I've flown had the ability to put in the exact MDA (or at least rounded to 10 feet) and the autopilot would level off there. So, I don't think it's a very accurate statement to say "most operators round up to the nearest 100 feet". Some do, many don't.

The other thing to consider is, in 2018, I would say that "most operators" aren't doing dive and drive approaches any longer.

On the CRJ, the MDA can select the MDA and it rounds to the nearest 10 feet, but the altitude selector in the autopilot has to be rounded up to the nearest 100 feet.

Does your company still train to do dive and drive?

No, constant angle non precision approach. Add 50ft to the MDA. There are some approaches that require a dive and drive such as the LOC/DME 15 in Aspen.

The POH/AFM/Autopilot supplement will state what the limits are for the autopilot, in other words, what you can use it for. if it says you can go down to MDA or DH, you can do exactly that. If there are any quirky limitations, they'll be stated.