Royal Air Force - DA or DH?

[judge11]

What's in vogue these days; decision height or decision altitude? And while I' at it, QFE or QNH?

[[email protected]]

Probably a combination of both - QFE/DH at military airfields (perhaps with the exception of Brize) and QNH/DA for civilian fields.

[Herod]

In the civvy world generally, QFE/DH went out many years ago. Going around in a modern jet from say a 200' DH to a 3,000' altitude involves button-pushing, and an extra level of complication. Not needed. In my airline, when we introduced modern (then) jets in the early nineties to replace the turboprops, it was "all change"

[DaveReidUK]

I thought this was going to be about haircuts ...

[[email protected]]

In the civvy world generally, QFE/DH went out many years ago. Going around in a modern jet from say a 200' DH to a 3,000' altitude involves button-pushing, and an extra level of complication. Not needed. In my airline, when we introduced modern (then) jets in the early nineties to replace the turboprops, it was "all change"
Ah yes, got to keep things simple for plank drivers :)

[Bob Viking]

It is purely a function of whether the approach is flown on QFE or QNH. DH for a QFE based approach and DA for a QNH based approach.

The debate between the relative merits of QFE vs QNH will rage forever I think. The fact is that QFE works well in the UK but not in many other countries. My personal take is that it is time for the UK military to make the transition to QNH. But what do I know.

BV

[[email protected]]

It's much easier in a modern glass cockpit to use QNH since you can usually set a bug or similar reminder on the altimeter tape rather than do mental maths but QFE has always made sense to me for an approach as you always know how high you are above your intended landing area.

[aw ditor]

Don't you eject' on QFE?

[Il Duce]

Until recently at an airfield in Lincolnshire, one type would operate on QFE in inches, another on QFE in hPa, another on QNH in inches and another on QNH in hPa. Nice to have some variety, I suppose.

[chevvron]

It is purely a function of whether the approach is flown on QFE or QNH. DH for a QFE based approach and DA for a QNH based approach.

The debate between the relative merits of QFE vs QNH will rage forever I think. The fact is that QFE works well in the UK but not in many other countries. My personal take is that it is time for the UK military to make the transition to QNH. But what do I know.

BV
They tried changing to QNH based procedures for military aircraft back in I think the mid/late '80s; lots of fanfare and briefings; then it suddenly changed back to QFE very quietly when an 'elderly gentleman' cocked it up.

[Mogwi]

Don't you eject' on QFE?

Yes, but the seat barostat operates on QNH (or possibly Standard Pressure Setting!). 🙂

Mog

[sangiovese.]

They tried changing to QNH based procedures for military aircraft back in I think the mid/late '80s; lots of fanfare and briefings; then it suddenly changed back to QFE very quietly when an 'elderly gentleman' cocked it up.

yep iirc yellow approach plates for QNH white for QFE….

[langleybaston]

Until recently at an airfield in Lincolnshire, one type would operate on QFE in inches, another on QFE in hPa, another on QNH in inches and another on QNH in hPa. Nice to have some variety, I suppose.

And the poor little millibar gone but not forgotten. Like Centigrade.

"If it not essential to change, it is essential to not change"

[Bob Viking]

I know it’s a divisive issue but I honestly think that, due to our expeditionary nature, it would make more sense to train pilots from day one that the runway is not always at zero feet. I know it’s easier that way but I think it is setting people up for failure. And apart from your downwind height in the circuit (and a check halfway round finals if you’re being good) when do (should) you actually look at the altimeter in training versus looking out the window anyway? If we’re talking stepdown heights and DA’s then what difference does it make if you read the bold face or non-bold face numbers on the approach plate? As long as you look at the correct one.

BV

[nipva]

Don't you eject' on QFE?
Trees followed by hedges entering my peripheral vision did it for me

[chevvron]

I know it’s a divisive issue but I honestly think that, due to our expeditionary nature, it would make more sense to train pilots from day one that the runway is not always at zero feet. I know it’s easier that way but I think it is setting people up for failure. And apart from your downwind height in the circuit (and a check halfway round finals if you’re being good) when do (should) you actually look at the altimeter in training versus looking out the window anyway? If we’re talking stepdown heights and DA’s then what difference does it make if you read the bold face or non-bold face numbers on the approach plate? As long as you look at the correct one.

BV
Ever since a I flew from Denham I realised how easy it was to mentally 'convert' to QNH.
Denham's elevation was 249ft + circuit height 750 ft = altitude 1,000ft; much easier to read that on your altimeter.

[H Peacock]

If you do lots of visual circuit work, then QFE is the way ahead; same heights regardless of where you go, so much easier!

Denham's elevation was 249ft + circuit height 750 ft = altitude 1,000ft; much easier to read that on your altimeter.

Well that works at Denham, but then it’ll be different numbers if you go elsewhere, not so if you fly QFE.

I’m sure the Reds could calculate their numerous gate altitudes for each display venue, but why would you not (as they do) simply use the datum QFE?

[Private jet]

QFE = "can't do arithmetic" possibly even in Latin....

[[email protected]]

QFE = "can't do arithmetic" possibly even in Latin.... Quo Fundus Erratum - less easy to F it up:E And yes I know it's not real Latin.......

[albatross]

Dumb Colonial but:
” Is not DA used for non-precision approaches and DH for precision ( ILS) approaches. You may not descend below a DA until you have “The Runway Environment” in sight but you decide at the DH whether to land or overshoot and you will descend slightly below the DH due to your downward momentum and inertia while initiating a missed approach.
In both cases referenced to QNH.”

[Il Duce]

Dumb Colonial but:
” Is not DA used for non-precision approaches and DH for precision ( ILS) approaches. You may not descend below a DA until you have “The Runway Environment” in sight but you decide at the DH whether to land or overshoot and you will descend slightly below the DH due to your downward momentum and inertia while initiating a missed approach.
In both cases referenced to QNH.”
DA (QNH) or DH (QFE) for precision approach, MDA (QNH) or MDH (QFE) for non-precision approach.

[vascodegama]

albatross-No-DA QNH, DH QFE

HP- I wonder what the reds did on the USA tour. Come to think about it what to the TBirds and Blue Angels do?

As for circuit work students at say KRND seem to manage. Virtually the all of the world uses QNH so why not move with the times (albeit belatedly). Even BZN has done so (a major challenge in itself).

ID beat me to the typing.

[albatross]

In over 45+ years i of aviating I have not even once been asked to use or even been given the QFE.
I do remember it being briefly talked about on various courses but only as an interesting historical aside.
Probably a good thing as I am so easily confused by new concepts and procedures. A problem often commented upon, sometimes in official writing and at great length, by various bemused instructors and examiners.

.albatross-No-DA QNH, DH QFE

HP- I wonder what the reds did on the USA tour. Come to think about it what to the TBirds and Blue Angels do?

As for circuit work students at say KRND seem to manage. Virtually the all of the world uses QNH so why not move with the times (albeit belatedly). Even BZN has done so (a major challenge in itself).

ID beat me to the typing.

[chevvron]

If you do lots of visual circuit work, then QFE is the way ahead; same heights regardless of where you go, so much easier!


Not necessarily. At a lot of civil airfields, visual circuit 'height' can vary due to various reasons not just NIMBYs.
Some airfields use 800ft QFE, some use 1000ft, some use 1200ft, some use a combination depending on whether single or multi engined.

[SASless]

OH LORD...NO!

Please let this die a quick death and spare us what is coming.

We have hashed this to death several times in the past.

Can we just accept the UK goes it alone on this as they do lots of interesting things in aviation.

That is their choice.....leave them to it.

[On Track]

Exactly. It is a purely British debate.

[throwaway1]

Brize uses QNH, everywhere else in the UK Mil appears to use QFE. AIDU plates have both (M)DA and (M)DH printed on them, though the altitude rather than the height is the primary.
When flying IF some quaint ATC chat remains at military airfields such as confirming the minima over the radio and “cockpit checks, report complete” whereas civvies just expect you to know what you’re doing and be ready (or say if you aren’t) and there aren’t differing instrument rating limits so just one minimum. Always confuses the exchange pilots.

[Il Duce]

There are many reasons why a controller needs to know what your DH, DA, MDH or MDA is, as well as knowing when your checks are complete. Time, space on this thread and my reluctance to explain prevent me from going into detail.

[Bob Viking]

Part of my logic for suggesting it is time for the UKMIL to make the switch comes from flying fast jets in many different countries. None of which use QFE routinely.

I will additionally admit that, on my first overseas tour (in Canada), my SOP ‘British Officer’ approach to IFR operations did not adequately prepare me for the rigours of operating a Hawk into large, international airports (San Fran Int, Chicago, Seattle and Calgary to name a few). In fact I would go so far as to say the ease and freedom with which we operate in the UK is pretty much unique for military operators worldwide. It is also worth noting that there are many airports where QFE just isn’t possible unless your altimeter can wind down a very long way (Rocky Mountain Municipal outside Denver was my highest at 5673’ AMSL).

I firmly believe we would serve our pilots better by introducing them to QNH from day one. After all, if you really need to know your height above ground most of our military aircraft are now Radalt equipped anyway.

The difference between DH/MDH and DA/MDA operations is minimal in practice. You have to remember a number and make a decision whichever you use. Your actual height above the ground at that point is no different so your ability to manoeuvre to make a successful touchdown is unchanged.

BV

[Brain Potter]

With QFE being an anachronism in the most countries, the term Decision Height is now usually associated with Low Visibility Operations where the vertical element of the approach minima is derived from radio altimeters. ILS Cat II DH is circa 100 ft, Cat IIIA 50ft and Cat IIIB usually NO DH.

[chevvron]

Brize uses QNH, everywhere else in the UK Mil appears to use QFE. AIDU plates have both (M)DA and (M)DH printed on them, though the altitude rather than the height is the primary.
When flying IF some quaint ATC chat remains at military airfields such as confirming the minima over the radio and “cockpit checks, report complete” whereas civvies just expect you to know what you’re doing and be ready (or say if you aren’t) and there aren’t differing instrument rating limits so just one minimum. Always confuses the exchange pilots.
I believe Northolt use QNH too.

[chevvron]

There are many reasons why a controller needs to know what your DH, DA, MDH or MDA is, as well as knowing when your checks are complete. Time, space on this thread and my reluctance to explain prevent me from going into detail.
No such requirment at civil airfields; pilots are expected to pre brief their minima and to carry out checks when convenient.

[[email protected]]

If you are wearing an RAF pilot's brevet in the cockpit you should be able to use either without any problem.

I taught a number of AAC pilots procedural IF and we used QFE at mil airfields (except Brize) and QNH at civ fields - and they all managed it very well.

[chinook240]

Brize uses QNH, everywhere else in the UK Mil appears to use QFE. AIDU plates have both (M)DA and (M)DH printed on them, though the altitude rather than the height is the primary.
When flying IF some quaint ATC chat remains at military airfields such as confirming the minima over the radio and “cockpit checks, report complete” whereas civvies just expect you to know what you’re doing and be ready (or say if you aren’t) and there aren’t differing instrument rating limits so just one minimum. Always confuses the exchange pilots.

Not everywhere else uses QFE, at least Odiham also uses QNH, there may be others?

[beardy]

It strikes me that pilots who habitually depart from and arrive back at the same airfield prefer QFE. Those that don't, prefer QNH possibly because it provides better awareness of terrain around the airfield and the effects of pressure altitude.

[chevvron]

Not everywhere else uses QFE, at least Odiham also uses QNH, there may be others?
Northolt as I said.

[[email protected]]

Northolt and Odiham's use of QNH will be because they are under the London TMA and it will avoid potential level busts changing late from QFE to QNH on the go around/departure.

[chinook240]

Odiham circuit is now within the enlarged Farnborough control zone. We’ve always had to coordinate with Farnbourgh arrivals and departures.

[judge11]

Thank you for all the replies. I had no intention to re-open (again) the QNH v QFE debate.

All I was after was that a demi-god from Central Fun School would jump in with chapter and verse from the METS syllabus.

Given that QFE is still generally used in the RAF, in the multi-crew environment, what is the phraseology in use? 'One Hundred Above'.........'Decide' (like wot i learnt) or a mongrolised version of the continental version 'Approaching Minimums'........'Minimums' followed by that ultimate in buck-passing - 'continue'.

[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.

[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]

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]

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]

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]

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

[chevvron]

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]]

Although someone might actually have to fly the aircraft briefly.

Nooo!!! :eek: 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? :E