Airbus speed as seen by controllers

[applecrumble]

I'm just wondering exactly what a controller will see on their radar display.
On the Airbus we can select a speed. I.e if we are asked to fly 290 exactly then we can select that. It's my understanding that ATC would be able to see this selection.
On the other hand we can fly a managed speed and in the decent it has a +/- 20kts window where the aircraft can vary its speed by plus or minus 20 knots to remain on the descent profile.
Does ATC see the exact IAS we are flying or just a GS read out in this situation?

[The Many Tentacles]

For London en-route, we see the IAS that the aircraft is flying, regardless of what you have dialled in. That said, if you've been told to do 250 and you're doing 280 expect a question.

We're also aware that the Airbus can go 20 knots each side to maintain the profile, but I believe that can be managed by the pilots if they're on the ball

[DaveReidUK]

Originally Posted by applecrumble

On the Airbus we can select a speed. I.e if we are asked to fly 290 exactly then we can select that. It's my understanding that ATC would be able to see this selection.

As above, IAS is a Mode S/EHS dowlinked parameter, so ATC can see it, but selected speed isn't, so they can't see that (though they can see selected altitude).

[OscarTango]

At Maastricht UAC, we see the actual IAS, and actual Mach #... During descent ( we are Enrique upper area), I tell the crew to keep a certain Mach # during descent (if I want to ground speed to increase) and to fly xxx knots on transition... And I'll keep an eye on it ;-)

[kontrolor]

we see both IAS and M, but we have opted for filtering (so up to FL245 IAS is displayed, above M)

[Del Prado]

It becomes less accurate the closer you are to the ground so even when a pilot says he's doing 160 to 4, Mode S often shows 145kts.

Fault especially evident on Orange 319s.....

[Captain Spam Can]

When you request 160 till 4 do you expect it until 4D or do you expect at 5D the aircraft will start to configure. I only ask because after 8 years I'd say 99.9% of my colleagues brief and will start slowing down (dropping the gear) at 5D.

[blissbak]

Originally Posted by Captain Spam Can

When you request 160 till 4 do you expect it until 4D or do you expect at 5D the aircraft will start to configure. I only ask because after 8 years I'd say 99.9% of my colleagues brief and will start slowing down (dropping the gear) at 5D.

Honestly it's not a matter of what we do expect but what you are supposed to do, to keep the speed exactly till the specified limit , 4DME.

To make a comparison, what's your behavior when asked to cross a VOR at FL100?

[DaveReidUK]

Originally Posted by Del Prado

Fault especially evident on Orange 319s.....

Slippery beasts (not just the Orange ones), by all accounts.

[tom775257]

As per an approach at Luton yesterday, 165 to 5 is much better IMHO on the A320 series than 160 to 4, no idea about other jets.

Typical 160 to 4. Option 1: Drop gear at 5, big increase in drag, speed lags well below 160, lazy autothrust over compensates, revs engines, now doing about 165-170 and drag decreases again as gear doors close, now at 4 miles, approach speed 'selected' (managed), now doing often higher than 160 at 4 and thus a rush to configure fully and meet stable approach criteria. Option 2: fully configure by 4, dragging it in with lots of noise and fuel burn. Option 3: Drop gear and 'select' approach speed at 5 miles figuring you are doing 160 within 4 point something miles and close enough for government work, with a nice quiet smooth approach for passengers and airport close inhabitants alike

[Del Prado]

I'm a big fan of option 3 myself, passing 4 dme at low 150's would seem like an excellent compromise.

Passing 4 dme at 126kts is clearly not.
Some of your colleagues are not doing it right (and it's not always Easy to be fair)

[Cough]

Or...Flap 3 approach - At 4.3d manage speed, gear down, flap full... Thrust stays pretty much at idle, hit 4d at 160 and it decelerates quickly after that (gear doors open etc)

[Captain Spam Can]

I drop the gear at 5d and just as the thrust comes on I manage the speed so I aim to be crossing 4.3 ish as its around 155kts. But I often think if I drop the gear, keep speed at 160 then at 4D finish configuring I'm going to screw the flow up as everyone else manages the speed at 5d so I'll catch the guy infront. I often wondered because to me 160 til 4 means 160 til 4 but I don't know anyone who leaves the speed selected and drags it in. Dropping the gear at 4d is too late/cutting it fine for our stable criteria to then select F3/Full.