Royal Air Force - DA or DH?

[Shameless]

This old debate is likely to finally be resolved. With the rollout of Military PBN (GNSS) in the UK we will finally make the move to QNH. It wouldn't make sense to mix QFE for Conventional Procedures with QNH for PBN.

[212man]

I would think using QFE causes issues with coupled aircraft, when changing the subscale whilst coupled to ALT? This happened in the North Sea in the 2000s when new technology helicopters arrived, and was the final decider for one operator to abandon its use. The alternative is convoluted SOPs.

[chevvron]

Originally Posted by Downwind.Maddl-Land

As an aside - Mil ATCOs are not allowed, or taught, to use speed control as a tool when establishing an arrival sequence. Therefore, the 'cockpit checks - report complete" is frequently used as a very coarse technique to get arrivals towards some sort of commonality in approach speeds to maintain a sequence.

Until about 1980, it was prefixed 'reduce to circuit speed and carry out cockpit checks etc...'

[H Peacock]

I would think using QFE causes issues with coupled aircraft, when changing the subscale whilst coupled to ALT? This happened in the North Sea in the 2000s when new technology helicopters arrived, and was the final decider for one operator to abandon its use.

Well potentially the same issue when changing between QNH and Std; not unique to using QFE.

Now some AFCSs in ALT will try to climb or descend the ac if the sub-scale is changed (certainly some Bombardier ac will), while others remain level regardless. That all said, the sub-scale would normally only be changed when descending or climbing to a new Alt, Ht or FL, ie not when intending to remain level.

[212man]

Originally Posted by H Peacock

Well potentially the same issue when changing between QNH and Std; not unique to using QFE.

Now some AFCSs in ALT will try to climb or descend the ac if the sub-scale is changed (certainly some Bombardier ac will), while others remain level regardless. That all said, the sub-scale would normally only be changed when descending or climbing to a new Alt, Ht or FL, ie not when intending to remain level.

I’d agree for changing from STD to QNH, so in V/S or similar, but I think changing to QFE is typically done while level.

[PlasticCabDriver]

Originally Posted by H Peacock

Now some AFCSs in ALT will try to climb or descend the ac if the sub-scale is changed (certainly some Bombardier ac will), while others remain level regardless. That all said, the sub-scale would normally only be changed when descending or climbing to a new Alt, Ht or FL, ie not when intending to remain level.

Sounds like the S-92. Pumas and 175 don’t do it.

[212man]

Originally Posted by PlasticCabDriver

Sounds like the S-92. Pumas and 175 don’t do it.

Yes because their parent has an airline background. Sikorsky has a “we have an 18000 transition altitude” helicopter background.

[[email protected]]

It wouldn't take a convoluted SOP to decouple ALT or V/S, change the pressure setting and then recouple.

Although someone might actually have to fly the aircraft briefly................

[H Peacock]

It wouldn't take a convoluted SOP to decouple ALT or V/S, change the pressure setting and then recouple.

No it wouldn’t! I’ve operated on mixed QFE/QNH ops for years. Nearly all sub-scale changes are combined with a change of alt/ht/FL, so if the AFCS is doing the work the only potential gotcha is in a Bombardier-type AFCS where you have to initiate the descent (or climb) in VS or FLC, then change the sub-scale. Certainly in the Global, if in ALT, the AFCS would follow a changed sub-scale - it became second nature to move the Alt Sel, initiate the descent, then change sub-scale.

Waddo RNP T&G to join necessitates a change to QFE in the upwind turn, you then level downwind at 1000ft QFE - simple!

Few occasions one may stay ‘level’ is perhaps on a handover between MATZs: “Set Conningsby QFE, adjust to 2500ft”

[Herod]

Although someone might actually have to fly the aircraft briefly.

Nooo!!! Shock, horror. You mean actual hand-flying? I don't think that's taught anymore.

[chevvron]

Originally Posted by 212man

Yes because their parent has an airline background. Sikorsky has a “we have an 18000 transition altitude” helicopter background.

Like we are about to do?
Maybe not 18,000 but Common Transition Altitude (CTA) is on the cards, getting rid of RPS. Problem is the EU; I think the UK CAA are pretty much agreed but as usual, the EU countries are dragging their heels about agreeing what it will eventually become.

[[email protected]]

Originally Posted by Herod

Although someone might actually have to fly the aircraft briefly.

Nooo!!! Shock, horror. You mean actual hand-flying? I don't think that's taught anymore.

Yep, all those vital hand-eye coordination skills we were tested for in the past - who needs 'em when you can just press some buttons?