Vertical path non-precision approach safety?

[Roger Roger]

@Zephyr thanks for bringing some real expertise to the thread.

 

[Autothrust Blue]

Bingo. Don't forget that THR HOLD is the same as IDLE CLMP and can bite you just the same. I'm willing to bet that is what bit the Asiana guys in SFO. I rode the throttles pretty good in the Boeings, too when I realized the same weak link existed.

Similarly, watch yourself in THR IDLE on fifi.

Not to mention that the effin' TLs don't move.

Bad human interface design is bad.

 

[jtrain609]

An unnecessary missed approach is less safe than landing....and any argument to the contrary is inane.

Might as well stop doing those dangerous CAT 3 approaches too... I mean, switching the pilots so low to the ground! Crazy!

Then why have stabilized approach criteria if getting it on the ground is the safest course of action?

View attachment 24999

Looks like we'd fly it to "ball note #2" and then pick up the visual.

At my employer, on my specific equipment (which means yours may differ in a variety of ways), that when we use the VPATH deviation, we're almost monitoring "Progress Page 2" for a numeric value of any VPATH deviation.

According to our procedure, if you're heads down after DA following either when you should be flying visual, you're making a potentially hazardous mistake -- because if the PM is heads-out monitoring your VPATH deviation that low, he's out of the loop and the PF is being a test pilot doing this own thing.

We don't even need the VNAV data to fly CANPA's.

On that plate, if we couldn't get the VNAV data to come up, we'd start a descent 0.3nm from REEBO at 700-800 FPM and go around at MDA + 75' if we didn't see the runway. The chart even tells you how fast to descend! If we have VNAV data, then great and we use it, but if not, we can still do a CANPA approach.

Thus, the -9's can still do this stuff.

 

[Autothrust Blue]

For reasons, it's better with some sort of VNAV. I'm not a fan of having a DA/DH without vertical guidance, as is the normal practice on the Brasilia. Sure you can do it in your head, but given the mass of the airplane and the normal rates of descent involved I personally consider 800-900'/min to MDA and drive an acceptable risk. But normally it's not necessary.

Edit: "normally" means when it's not SCT003 and the MDH is 300'.


SSSSSSEENT FFFFROMM FMS KEYBOAAAAAAARDDDDD

 

[dasleben]

Depends on the aircraft and operator. On our E190s it's a captain maneuver down to 50' RA mins. There's no control change. The captain hand flies the whole maneuver turning off the autopilot by 800 feet using the HUD.

Forgive me, but I forget if it's Cat IIIa, b or c. It's whichever is not auto land, and down to 50'.

Then you, sir, are the "limited exception."

 

[jtrain609]

For reasons, it's better with some sort of VNAV. I'm not a fan of having a DA/DH without vertical guidance, as is the normal practice on the Brasilia. Sure you can do it in your head, but given the mass of the airplane and the normal rates of descent involved I personally consider 800-900'/min to MDA and drive an acceptable risk. But normally it's not necessary.

Edit: "normally" means when it's not SCT003 and the MDH is 300'.


SSSSSSEENT FFFFROMM FMS KEYBOAAAAAAARDDDDD

Again, we can't drive.

Additionally, our charts tell us the altitude we're supposed to be at each mile so it's kind of idiot proof. As in, I did one in the sim recently, and the glide path looked like an ILS.

 

[BobDDuck]

Again, we can't drive.

Additionally, our charts tell us the altitude we're supposed to be at each mile so it's kind of idiot proof. As in, I did one in the sim recently, and the glide path looked like an ILS.

Are your charts baro compensated?

 

[PhilosopherPilot]

Then you, sir, are the "limited exception."

How limited is it? I'm looking into it, as I'm curious who operates Cat III without autoland now.

 

[PeanuckleCRJ]

Not to mention that the effin' TLs don't move.

Bad human interface design is bad.

Be a man and turn them off. It's easy just to look over at the screens when it's engaged.

 

[PeanuckleCRJ]

I thought of "THR HOLD" as "We're not going to move any more in this vertical mode" and "CLMP as XX-Manual Positioning"

Keep an eyeball on that TARP panel because, after all, whether you're flying the steampunk DC-9-15 or a 717, it's an after-market mod'd DC-9.

CLMP and THR HOLD are the exact same thing and come about with the exact same logic. Just the Douglas throttles are less smooth. The modes and gotchas are identical, though.

 

[PeanuckleCRJ]

Then you, sir, are the "limited exception."

Most HGS operators are CAT III handflown certified. DL 737s, all of WN 737s...

 

[dasleben]

Most HGS operators are CAT III handflown certified. DL 737s, all of WN 737s...

FINE.

 

[BobDDuck]

CLMP and THR HOLD are the exact same thing and come about with the exact same logic. Just the Douglas throttles are less smooth. The modes and gotchas are identical, though.

I don't think they are on the 717. In CLMP you can move the thrust levers with no resistance from the autothrottle. In THR HOLD you have to fight the autothrottle servo (slightly) to move the levers. The logic is the same though, as you say.

 

[seagull]

CLMP and THR HOLD are the exact same thing and come about with the exact same logic. Just the Douglas throttles are less smooth. The modes and gotchas are identical, though.

Depends on which "Douglas" you refer to, the -11 is very smooth.

 

[derg]

An unnecessary missed approach is less safe than landing....and any argument to the contrary is inane.

Might as well stop doing those dangerous CAT 3 approaches too... I mean, switching the pilots so low to the ground! Crazy!

We have to be configured, on-speed, on glidepath

I don't think they are on the 717. In CLMP you can move the thrust levers with no resistance from the autothrottle. In THR HOLD you have to fight the autothrottle servo (slightly) to move the levers. The logic is the same though, as you say.

And I forgot the wonderful "LO LIM" mode too.

 

[BobDDuck]

And I forgot the wonderful "LO LIM" mode too.

Is that straight from the -9? If so I'm impressed that it had low speed protection going back that far. That's one I'll (hopefully) only see in the sim, but it is kind of cool watching it slam the thrust levers up.

 

[PeanuckleCRJ]

Is that straight from the -9? If so I'm impressed that it had low speed protection going back that far. That's one I'll (hopefully) only see in the sim, but it is kind of cool watching it slam the thrust levers up.

LO LIM is not low speed protection. LO LIM is as close to idle as the AT would let the thrust levers go (in certain modes) to prevent unspooling issues. You had to then reach over and manually back them the rest of the way to idle if so desired.

None of the DC-9s had active AT, so that's not applicable there.

 

[PeanuckleCRJ]

Depends on which "Douglas" you refer to, the -11 is very smooth.

Good point. You have to always always always babysit the AT on the MD-88/MD-90.

 

[derg]

Is that straight from the -9? If so I'm impressed that it had low speed protection going back that far. That's one I'll (hopefully) only see in the sim, but it is kind of cool watching it slam the thrust levers up.

Nah, that just means that the autothrottles don't have the authority to retard them any lower in your phase of flight.

So if you're descending at 250 and commanding a 2500 fpm descent in V/S, it's probably going to respect your V/S request, give you "LO LIM" on the auto throttle status and slowly accelerate unless you pull the throttles back manually.

 

[BobDDuck]

Nah, that just means that the autothrottles don't have the authority to retard them any lower in your phase of flight.

So if you're descending at 250 and commanding a 2500 fpm descent in V/S, it's probably going to respect your V/S request, give you "LO LIM" on the auto throttle status and slowly accelerate unless you pull the throttles back manually.

Ah... I honestly don't know if that's a thing on the 717. There is no mention of it in the systems manual we have and I don't remember reading about it in a CBT anywhere. I know it will go full idle when you pull select a lower altitude. I'll have to try it in V/S and see what happens.

EDIT: That said, your systems manual is sadly lacking so it's entirely possible we have LO LIM as well.