Why do the RAF still use QFE?
Wholi', some of the modern toys are so clever that they can provide an altitude indication using methods less crude than GPS height.
Given the present position of the aircraft, a 3-D geographical database knows the elevation of the immediate terrain and and can apply the radalt (radio usually, not radar) indication to that to obtain an altitude amsl. The problem, though, is that whilst this is probably pretty accurate, altimeters work on ISA lapse rates etc as a standard, so everyone must 'speak the same language' - particularly in RVSM airspace. But this 3-D geo-database information can at least be used to set the CCWR scanner tilt to the optimum value, avoiding the need for barely-trained people-tube co-piglets to learn the art of weather radar control....
One of the 'Sandymount set', perchance?
Given the present position of the aircraft, a 3-D geographical database knows the elevation of the immediate terrain and and can apply the radalt (radio usually, not radar) indication to that to obtain an altitude amsl. The problem, though, is that whilst this is probably pretty accurate, altimeters work on ISA lapse rates etc as a standard, so everyone must 'speak the same language' - particularly in RVSM airspace. But this 3-D geo-database information can at least be used to set the CCWR scanner tilt to the optimum value, avoiding the need for barely-trained people-tube co-piglets to learn the art of weather radar control....
The radar altimeter indications are going to be rushing up and down like the drawers of a lady I once knew at RAF Valley, but even faster (if that were possible).
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Aaaaah BEagle - - - I knew I was getting old and out of touch mate!!!
But I still had more fun than most folks can even dream of nowadays.
PS: you might be right in your guess!
But I still had more fun than most folks can even dream of nowadays.
PS: you might be right in your guess!
What do you mean Wholigan? Fun, its supposed to be fun!! Just don't tell them that!
They might all want to do it!!
For me QFE works just as well as QNH! It just depends on how fast your going!!
The only rule is don't hit anything! Something we both know about!!
Off to the bar with flack jacket and a bottle of Grouse!!
PS Beagle
Was it Lockjaw or Pannel Beater?
They might all want to do it!!
For me QFE works just as well as QNH! It just depends on how fast your going!!
The only rule is don't hit anything! Something we both know about!!
Off to the bar with flack jacket and a bottle of Grouse!!
PS Beagle
Was it Lockjaw or Pannel Beater?
At least when using QNH you know your height in relation to the the MSA, no mental gymnastics required. In the company I work for, we only set the DH on the rad alt when carrying out a CAT2 or CAT3 approach, because outside of these parameters, 100/50', the rad alt is not reliable because the terrain is not constantly level! You do get used to making all decisions with regard to altitude using airfields as diverse Amsterdam and Munich. It must only be the military that do not have a means of setting the pressure setting in inches or Mb on their altimeters. But then what do I know!
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Occasional Aviator,
True, GPS is not accurate, that is, for civilian use. Because it was intentionally designed like that. Yet all military GPS signal use precision code which has a scary accuracy of just within 2ft.
Knowing the accuracy of the GPS height channel
Last edited by C-N; 7th Sep 2009 at 04:25.
Cunning Artificer
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Beags, you forgot to add that the EGPWS, just like GPWS before it, also reads out the height above ground during final approach, just like a well trained PNH (or NHP, take your pick)
Minimums, 50... 40... 30... 20... 10...
...and of course it also shows you all the lumpy bits ahead, if you decide to do a go-around and shouts at you like a real instructor if you don't pay attention.
Minimums, 50... 40... 30... 20... 10...
...and of course it also shows you all the lumpy bits ahead, if you decide to do a go-around and shouts at you like a real instructor if you don't pay attention.
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just like a well trained PNH (or NHP, take your pick)
Love the comment below (page 2, IIRC) that the RAF does not understand the difference between QFE/QHN/RPS! How rude!
Wholigan,
"The radar altimeter indications are going to be rushing up and down like the drawers of a lady I once knew at RAF Valley, but even faster (if that were possible)."
I knew her too....
"The radar altimeter indications are going to be rushing up and down like the drawers of a lady I once knew at RAF Valley, but even faster (if that were possible)."
I knew her too....
In the biblical sense?
Not to cast any doubt on the young lady's virtue or besmirch her character, but what became of Jane-Anne....?
Not to cast any doubt on the young lady's virtue or besmirch her character, but what became of Jane-Anne....?
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LM, the V-Force Radio Altimeter, a Mk 5 IIRC, went to 5000 feet. The Radar Altimeter, the Mk 6, went to 60,000 feet. It was a bit shabby below 500 feet.
The pair gave interesting and conflicting readings. The Mk 5 used to echo off the ground, the Mk 6 off the top of the tree canopy. Not good with 250 ft tall trees in the jungle.
The pair gave interesting and conflicting readings. The Mk 5 used to echo off the ground, the Mk 6 off the top of the tree canopy. Not good with 250 ft tall trees in the jungle.
If learning command and FJ bases want to fly QFE to make the circuit easier that's up to them. Personaly, I think Brize and Lyneham should use QNH. A moden FMS's VNAV function is designed to work on QNH, everywhere else in the world uses QNH so why have your home base the only place where you do it differently.
The danger lies where Civ / Mil traffic is using different pressure settings in the same airspace (as can happen at Brize when a charter requests or is given a QNH approach.)
Or when you're a bit knackered and can't remember whether or not today's approach minma is the one in bold writing.
Plus, Sector saftey is an Altitude. I've heared it briefed hundreds of times but never seen anyone actualy apply a correction for airfield elevation when they declare that they're through S.ALT. climbing out with QFE set.
Do what the rest of the world does, they generaly have more experience!!
The danger lies where Civ / Mil traffic is using different pressure settings in the same airspace (as can happen at Brize when a charter requests or is given a QNH approach.)
Or when you're a bit knackered and can't remember whether or not today's approach minma is the one in bold writing.
Plus, Sector saftey is an Altitude. I've heared it briefed hundreds of times but never seen anyone actualy apply a correction for airfield elevation when they declare that they're through S.ALT. climbing out with QFE set.
Do what the rest of the world does, they generaly have more experience!!
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C-N
Well, yeees, but only when
a) it's available and not being jammed, and (more importantly)
b) it is in its normal operating parameters and not within one of the known or possible failure modes which could give you bounded or unbounded errors without indications of failure.....
Yet all military GPS signal use precision code which has a scary accuracy of just within 2ft.
a) it's available and not being jammed, and (more importantly)
b) it is in its normal operating parameters and not within one of the known or possible failure modes which could give you bounded or unbounded errors without indications of failure.....
I dont understand the request and i usually ignore it anyway.
Do you know what else is in the area? Do you know what height they are descending to? Whether they are using QFE, which as the service is being given by an RAF unit all the military operators are likely to be using?
May I suggest if you don't understand then you ask, either on the radio there and then, or by land-line later!!
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You ask for a service (25 miles from the radar head) and they ask you to set the QFE (something I find very surprising) and you ignore the request
You get told to speak to lossie by ABZ when you start heading over westwards. And when I say told I mean told. If you decline the offer you then get it restated that they want to talk to you.
If you do then speak to them they will try and keep you at sub 2000 ft and remaining 20 miles to the south of Lossie and Kinloss. If you then decline that offer due to such technicalities of actually having a chance in hell of pulling off a forced landing, busting rule 5, generally getting the poo kicked out of you with the turbulence with the highish ground that they want you to fly over or of course remaining VFR. They then go to phase 2 of controlling you in class G airspace. Which is invent traffic in front of you and give you an immediate avoiding action due unknown traffic, of course moving you to the south where you didn't want to go. It works a few times then you spot the real reason for them wanting to move you is the circuit at Kinloss and they are trying to maintain radar sep on the circuit while keeping 3000ft clear for the instrument procedures. They control you in class G to try and maintain a exclusion zone way outside thier CMATZ.
So I completely know where the poster was coming from. And setting QFE is the least of your worries after accepting a "service" off lossie radar.
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Mad Jock
Don't ask for a DS! The Lossie Controllers may give you TI but you just keep your eyes peeled. Or just Sqk 7000 and carry on your merry way using the 'see and avoid' principle. You don't have to do what 'they' say.
Simples
Don't ask for a DS! The Lossie Controllers may give you TI but you just keep your eyes peeled. Or just Sqk 7000 and carry on your merry way using the 'see and avoid' principle. You don't have to do what 'they' say.
Simples