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Royal Air Force - DA or DH?

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Royal Air Force - DA or DH?

Old 17th Oct 2022, 10:23
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Royal Air Force - DA or DH?

What's in vogue these days; decision height or decision altitude? And while I' at it, QFE or QNH?
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Old 17th Oct 2022, 11:18
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Probably a combination of both - QFE/DH at military airfields (perhaps with the exception of Brize) and QNH/DA for civilian fields.
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Old 17th Oct 2022, 11:58
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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"
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Old 17th Oct 2022, 12:00
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I thought this was going to be about haircuts ...
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Old 17th Oct 2022, 12:40
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Originally Posted by Herod View Post
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
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Old 17th Oct 2022, 12:41
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Judge

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
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Old 17th Oct 2022, 12:49
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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.
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Old 17th Oct 2022, 13:33
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Don't you eject' on QFE?
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Old 17th Oct 2022, 13:34
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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.
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Old 17th Oct 2022, 13:47
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Originally Posted by Bob Viking View Post
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.
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Old 17th Oct 2022, 13:49
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Originally Posted by aw ditor View Post
Don't you eject' on QFE?
Yes, but the seat barostat operates on QNH (or possibly Standard Pressure Setting!). 🙂

Mog
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Old 17th Oct 2022, 14:04
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Originally Posted by chevvron View Post
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 QFEÖ.
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Old 17th Oct 2022, 14:16
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Originally Posted by Il Duce View Post
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"
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Old 17th Oct 2022, 14:23
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Chevvron

I know itís 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 itís 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 youíre being good) when do (should) you actually look at the altimeter in training versus looking out the window anyway? If weíre talking stepdown heights and DAís 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
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Old 17th Oct 2022, 14:44
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Originally Posted by aw ditor View Post
Don't you eject' on QFE?
Trees followed by hedges entering my peripheral vision did it for me
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Old 17th Oct 2022, 16:02
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Originally Posted by Bob Viking View Post
I know itís 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 itís 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 youíre being good) when do (should) you actually look at the altimeter in training versus looking out the window anyway? If weíre talking stepdown heights and DAís 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.
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Old 17th Oct 2022, 17:59
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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 itíll be different numbers if you go elsewhere, not so if you fly QFE.

Iím 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?
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Old 17th Oct 2022, 18:29
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QFE = "can't do arithmetic" possibly even in Latin....
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Old 17th Oct 2022, 18:37
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Originally Posted by Private jet View Post
QFE = "can't do arithmetic" possibly even in Latin....
Quo Fundus Erratum - less easy to F it up And yes I know it's not real Latin.......
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Old 17th Oct 2022, 18:48
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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.”

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