Flap speed references on PFD

[Will]

JHW, let me second your nod to the complexity of aviation systems. I think it's something that people are always underestimating. Even if we could coax Joe Sutton(*) out of retirement, we'd still have unanswered questions.

After MH370 disappeared, people started looking into the "pings" that the engines were sending to Inmarsat. I asked a friend of mine, who is a current 777 pilot, what he knew about engines communicating with satellites. His answer: he had no idea that that even happened. There are plenty of things about the airplanes that they don't even bother telling the flight crew.


*) Lead engineer on the 747 development project for Boeing

[IefCooreman]

As far as I'm aware, you can put any flap setting, with any speed you'd like (within certain limits) Just tick it, insert on the approach page, and you're set. Completely independent from the suggested speeds for the standard flap settings. These selections don't influence the maneuvering speeds, not that I'm aware off...

What happens if you haven't selected a flaps setting with appropriate speed? You don't get maneuvering speeds anymore?

[Britjet]

I said I would "phone a friend"...a senior BA Training Captain Examiner..
Here's his reply...

"You are correct in your recall that on BA 747s the flap speeds relate to V2 for departure and Vref 25 for the approach if  F25 speed is in the appr ref page. This is why we had to adjust the hold speed( if planning a F25 landing) as that is defined as Vref 30 + 80.
Boeing had a mod that BA chose not to pay for that referenced the flap speeds to Vref30 for the approach regardless of the flap used for landing.
Therefore both you and the simulator guys are correct. If the PSX simulator is for  a BA 747 then the flap speeds should be referenced to the Vref on the App ref page. Any other 747 then the PSX set up would be representative of most 747s assuming they had the Boeing mod."

End quote...

------

I presume the Mod was a fuel-saving measure. So some 747s use F30 min speeds only and some use both!

Brit

[John H Watson]

As far as I'm aware, you can put any flap setting, with any speed you'd like (within certain limits)

On our aircraft, the limitation was valid 744 flap detents (0, 1, 5, 10, 20, 25 & 30) and airspeeds 100~250kts

[Hardy Heinlin]

Hi Britjet,

I conclude this is an airline option :-)

Does anybody want me to make this feature optional instead of fixed installed?


Cheers,

|-|ardy

[Phil Bunch]

Given the presence of this and so many other uncertainties, how does anyone comfortably and with adequate certainty fly an airliner!?

These discussions have made me less comfortable as an occasional passenger - the last things I would want are (1) pilots with excessive (?) complexity, uncertainty, and ambiguity, (2) lack of access to software updates due to cost, and failure paths that are preventable.

[Hardy Heinlin]

Might be a bit too off-topic? How about an extra thread? :-)

[torrence]

Well, Phil

Most of these things such as the flaps speeds are relatively fine points dealing with 'best practice procedures', cost and maybe maintenance issues rather than safety margins for instance.  But I get your point relative to the pure complexity and uncertainties.  The Airbus tragedy a few years ago and the 777 crash at SFO more recently  illustrated the dangers of crew not understanding (or being trained for) the interactions of all the automated features of these aircraft.  

Cheers,
Torrence

[Phil Bunch]

I think a separate thread is appropriate - sorry for not thinking of that myself.

[Britjet]

I think it would be nice as an option - but then I am biased!
Brit

[HercMighty]

options are always good if easily managed  

[Sylle]

Some discussion on this subject found in the B747 symposium at smartcockpit.com

21. Flaps 25 vs. 30 landing, why do reference speeds change? In 767 all speeds are reference to F30, inconsistent for 747.

When the 747 Classic was developed, it was a Vref airplane. There was only one Vref chart. When the Vref was increased because of non-normal conditions, all the flap speeds, which were based on the Vref, changed also.
When the 767/757 was developed, Vref30, Vref25, and Vref20 were developed. The maneuvering speeds are referenced to Vref30. If the landing speed is increased because of a non-normal, the various flap speeds do not, because they are still based on Vref30.
When the 747-400 was developed, to maintain as much commonality with the 747 Classic as possible, the flap speeds were based on the reference speed. If the reference speed, whether Vref30, Vref25, is increased because of a non- normal, the flap speeds increase the same amount. This copies the 747 Classic, instead of the 757/767.

S.

[Hardy Heinlin]

Hello, old thread.

(Note: The above posts are 5 years old.)

Can anybody tell me whether BA still put their flap speed schedule on Vref25 if flap 25 is selected on the APP REF page? *

Quote from 2014:

I said I would "phone a friend"...a senior BA Training Captain Examiner..
Here's his reply...

"You are correct in your recall that on BA 747s the flap speeds relate to V2 for departure and Vref 25 for the approach if  F25 speed is in the appr ref page. This is why we had to adjust the hold speed( if planning a F25 landing) as that is defined as Vref 30 + 80. ..."

"... we had to adjust the hold speed ..." -- Is the hold speed adjusted automatically by BA's FMC modification or manually by BA's pilots?

I'm asking because the VREF basis is also relevant to the missed approach climb speed in the NG FMC (which BA installed after 2014).


Thanks!

|-|ardy


* Other airlines always put them on Vref30 even when a flap 25 landing is selected. In PSX there's an option checkbox for this on Instructor > Model > FMS. I think this checkbox should be deselected on BA models only.

[Hardy Heinlin]

For example: Overweight emergency landing ...

(BA 744 with NG FMC)

APP REF page, line 4R is set with 25/192 (VREF30 in line 2R indicates 184).

Go around ... VNAV SPD ... MCP SPD window blank ... climbing ...
now flaps are up and max flap speed limit is out of view ...
Where has the FMC put the (flap up) speed bug? On 272 or on 264? (Vref__ + 80)
(On non-BA aircraft the green UP bug and the magenta command bug would be on 264 as the landing flap setting will not influence the flap speed values.)

Some minutes later on missed approach cruise: If there's a hold on this missed approach and the hold is now active, where will the FMC put the bug then? On 272 or on 264? (Vref__ + 80)

[Britjet]

Hi Hardy,
As you know I'm a little out of date these days and becoming increasingly so, although I suspect I'll outlast the BA 747s!
For the non-normal procedure you quote you would select Flap25 on the APP REF page, but then manually insert the Flap 30 VRef after it - so it would have read 25/184.
For a subsequent go-around (and I can't remember ever doing it) it is my understanding that the UP bug would be on 272, as is the BA way, presumably due to the associated programming.
The subsequent hold would also have the up bug on 272, as I understand it.
The crew would be "allowed" to fly the hold (but only in the hold, not straight flight, interestingly enough) at the specified hold speed on the HOLD page, which is still predicated  on VRef30, so 264.
It's a bit of a bodge, for sure - I'm afraid I don't know what happens now, particularly in light of the NG FMC, which BA now uses.
I know we have some BA Pilots on the forum and can contact elsewhere, so either they can post or I can try to find out.
Peter.

[Hardy Heinlin]

Hi Peter,

thanks for the tip ("272"). It agrees with my theory which I just added in the next PSX update.

Yes, I got some good tips from BA pilots. The problem is: When you guys are in the sim or on the real ship you will open the MCP SPD window or set your own SEL SPD in such scenarios; so it's rather difficult to get a good occassion to test these unusual details ... :-)


Cheers,

|-|ardy

[jackTer]

I hate this IPAD spell-checker!

On the Settings screen of the iPad, select General and then Keyboard. Next to Auto-Correction, switch the on button to off.

[Britjet]

Thanks very muv Jack!
Prter