Royal Air Force - DA or DH?
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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?
"Mildly" Eccentric Stardriver
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"
Originally Posted by 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"
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
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
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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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.
Originally Posted by 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
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
Originally Posted by chevvron
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.
Originally Posted by 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.
"If it not essential to change, it is essential to not change"
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
BV
Originally Posted by 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
BV
Denham's elevation was 249ft + circuit height 750 ft = altitude 1,000ft; much easier to read that on your altimeter.
If you do lots of visual circuit work, then QFE is the way ahead; same heights regardless of where you go, so much easier!
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?
Denham's elevation was 249ft + circuit height 750 ft = altitude 1,000ft; much easier to read that on your altimeter.
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?
Originally Posted by Private jet
QFE = "can't do arithmetic" possibly even in Latin....
And yes I know it's not real Latin.......
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.”
” 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.”
