Adlerdriver

Thanks for the great info.

I'm confused by the bold above, since I've never seen either of those FMAs and IAN is not referenced in any of the Boeing manuals I've used. Would it be more accurate to say, "all Boeing production aircraft are IAN capable IF the operator buys that option"?

cougar

Yes IAN is a customer selectable option. For the 747-8 it is an FMC OPC pin selection, which is no cost. However, other Boeing production aircraft may not include IAN as a standard configuration. Also, I forgot about the 767, which doesn't have an option for IAN capability to my knowledge.

FedEx 777s do not have IAN enabled?

pangolin

We don’t set the bottom altitude or MDA in the autopilot. In the last descent to MDA we set the missed altitude. At minimums we go around.

Adlerdriver

No they don't.

Airbum

Just a question, do pilots just have to remember the min alt?

We set the LNAV/VNAV minimum in the FCP altitude capture window on the MD11 at my airline. personally I like it that way. If you become distracted the FD/Autoflight levels the aircraft and will not fly itself into the ground.

Going above the projected decent path angle in my mind is much less a risk then a decent below minimums. Both require the pilots to make a mistake. One just has a much higher chance of killing you.

Adlerdriver

So, do you worry about getting distracted on an ILS? On theses non-precisions, you set a DA or DDA in the baro mins and you have the same PFD indications of approaching mins and mins as an ILS.
You’re really worried about getting distracted on a non-precision approach and letting the aircraft “fly itself into the ground”? That’s a long time to be distracted.

Airbum

I figured somebody would bring up the ILS, and you have a great point. In regards to being distracted for a long time someone posted above that the ROC for obstructions was 250' at MDA. With a VVI of close to 1000 a minute at max weight to me that's not a lot of time.

If able I don't want to give up the safety factor of a MDA backup. I know what I would choose, to set a DA/MDA. Perhaps I just am so used to it after decades of non ILS approaches I am reluctant to change. It seems most airlines do what you are talking about. Why did I waste all those brain cells figuring out a VDP!

The other point is a lethal accident we had where a crew impacted terrain short of the runway. If they had the autopilot on and a MDA set instead of a MAP perhaps things would have been different.

pangolin

Both pilots set the mda. A blue line appears and the airplane says “minimums” when it occurs. If the two sides are set differently the airplane says minimums going through the higher of the two altitudes.

Adlerdriver

For now, until the issues with the MD-11 923 FMS software get sorted out, you really don't have the option set anything other than MDA. The downside, IMO, to setting the MDA is you can't get to the actual DA/DDA while staying on the calculated glidepath with the autopilot on. As soon as the A/P begins the level off (~200' above mins, typically) you're going missed. Why compute a VDP? - so you can see, as you're starting to level off at MDA, yup - it's behind me now, so I have zero change of landing out of this.

So, if you want to fly right down to DA while remaining on path, you've got to disconnect the A/P no later than 200' above mins. If you decide to go missed at mins, now you get to hand fly the missed approach. Not a big deal but I think most guys would prefer the option to keep the automation on, especially with all those thrusties and a low MAP altitude, complex route or both.

Once MD-11 operators have the choice, I guess you have to balance the perceived benefit of the A/P leveling off at MDA on an approach you now probably can't land out of anyway with being able to automate down to mins and beyond whether you decide to land or miss.
As far as the accident - MDA in the window might have helped. But, setting a descent floor and pre-programming mins is a procedural way to fly the approach and our clearance properly. To be blunt, it's not done to give us the leeway to so poorly execute an approach that the only reason we don't kill ourselves is because the A/P saves us.

cougar

This is the epiphany I had about 20 years ago when I first started instructing on Boeing aircraft. The whole concept of a CDFA is that the airplane arrives at the MDA at the VDP simultaneously, therefore the VDP is rendered an atavistic term from the dive and drive days.

Further, since the DA/DDA is coincident with the VDP when using CDFA procedures, any level off at minimums likely leads to an unstable approach due to immediately being high relative to the intended glide path. This in my view is a far greater risk than forgetting and flying through minimums. As Adlerdriver pointed out, we seem to remember minimums just fine on ILS approaches. Moreover, the “approaching minimums” and “minimums” call outs are available as automated calls.

Training is the foundation for CDFA procedures, to ensure crews understand that once the descent has started at the FAF, there is no change, no ‘getting down early” etc. Maintain the briefed descent mode/rate, once at minimums (DA/DDA), continue if runway environment is in sight, or go-around.

For example, all Non-ILS approaches on the 747-400 can be flown in VNAV, therefore VNAV PTH is the required FMA from the FAF until the End of Descent point per our company procedures. If the FMA changes from VNAV PTH to any other mode inside the FAF, it requires a go-around.

If V/S is required to fly the approach (this would only be necessary due to some NOn-normal), then once the calculated V/S descent rate is set at the FAF, is doesn’t change. At DDA, continue or go-around.