QFE question

Set that on your altimeter, you know it is right if AGL needle is at zero. Really it is that simple.

True. But almost the same could be said about QNH. ;)

When holding short of the runway, make sure the altimeter shows the runway's known elevation MSL. Assuming steady air pressure throughout the region that the flight will be conducted in, this one QNH setting will be valid for the entire flight, and for every airport.

QFE on the other hand only really works for that one particular reference spot on the ground.

As far as I know, most (all?) aviation charts will show the elevation of obstacles in relation to MSL. Since altitude derived from QNH is also in relation to MSL, it's quite simple: obstacle at 1500 ft? Fly 2500 ft high for a solid 1000 ft clearance. Approach and departure charts also show altitudes above MSL. 8000 ft at 12 DME? Well, just make sure to be at 8000 ft barometric 12 NM from the runway, simple as that. ;)

It takes a little getting used to landing at altitudes above 0 (1850 ft in case of Nellis), but IMHO QNH is more intuitive in every other aspect.

QFE is nice for local VFR flights. I think it makes less sense in IFR, and I'd never want to use it in IMC. That's purely my sim flying experience, though.

QFE is nice for local VFR flights. I think it makes less sense in IFR, and I'd never want to use it in IMC. That's purely my sim flying experience, though.

I don't understand how QFE would be any useful in VFR since the runway should be visible and as you mentionned, altitudes are given in MSL on airdrome and regional charts. When flying IRL, I have never used QFE and the tower never gave me any QFE setting. That said, I only have 11 hours of flight under my belt as PIC so I'm not pretending I'm the guru of aviation either... :)

Suggest to re-read what Yurgon posted. The key is local VFR.

When you are doing circuits at your local airfield it's quite common to use QFE.

Funny thing is, that's what I did, most of the time. And I never ever had to use QFE. Always used QNH.

It's quite funny that someone with 11 total hrs is using 'never ever' and 'always' ;)

I am talking about my own experience. That's all. I don't know what you find funny about it. :huh:

Much of this depends on the country in which you fly. In the UK if you'll be given QFE if you're remaining in the circuit, QNH if you're leaving the circuit (even if you're returning to the same field). If you've left the circuit you'll be issued QFE on approach to the circuit.

I've also flow in the US, and the instructor there hadn't even heard of QFE. Probably because field elevation was ~3000ft, and setting QFE would take an awful lot of turning of the pressure setting knob!

USAF is the only operator of the A-10 and only uses QNH-type altimeter settings. The hardware of the airplane is based on QNH use. Taking off with a different setting miscalibrates the systems.

In airliner civil space (say long transits) the A-10 would reference pressure flight levels like any other airplane. When in the combat arena the altimeter would once again be set QNH to reference altitude at any height.

The tower can tell you QFE info if it wants but in most airplanes/operators in DCS it should be ignored.

I had an issue recently with 2.0 red flag. I was used to the settings for 1.5 of 2986 or what ever, the atc now says 2806, now should I be trying to match that? it takes a lot of adjustment to get down to 2806 and 0 on the altimeter. Thought I was fine, later in the mission im trying to drop '97's on some bad boys, and I get the fuzing error, even though I always do adjust the HOF before hand along with adding the laste info into the cdu. Im a little confused about this.. ?

Don't set QFE in the A-10C, doing so is not realistic (setting QNH is required in reality to calibrate the IFFCC on takeoff) and will cause issues like you're seeing will weapon delivery in areas with terrain elevations significantly above MSL, especially where there are major elevation changes such as mountains.0

QFE works well when flying VFR in very localised areas and with terrain elevations close to MSL (such as most of Europe) it doesn't work well in other situations.

Don't set QFE in the A-10C, doing so is not realistic (setting QNH is required in reality to calibrate the IFFCC on takeoff) and will cause issues like you're seeing will weapon delivery in areas with terrain elevations significantly above MSL, especially where there are major elevation changes such as mountains.0

 

QFE works well when flying VFR in very localised areas and with terrain elevations close to MSL (such as most of Europe) it doesn't work well in other situations.

Eddie, thanks for the reply. What adjustments should I be making or leave well alone in regards to the altimeter?

What adjustments should I be making or leave well alone in regards to the altimeter?

IMO, set QNH prior to take-off and you're good to go, that is: set the runway's elevation AMSL (in Nellis that's around 1850 feet).

If you want to practice realistic procedures, pick an altitude as your transition altitude, and every time you climb above it, set altimeter to Standard (29.92 inHg), and then every time you descend below it you set it back to your previous QNH setting (using transition altitude as transition level isn't 100% accurate, but for starters it should be sufficient :thumbup:).

Eddie, thanks for the reply. What adjustments should I be making or leave well alone in regards to the altimeter?

I think proper QNH is set by default when you start a flight in DCS. However if you have a doubt, the QNH value is also written at the bottom of the briefing window.

With all my real-life flying done in the RAF, where QNH was the norm for local circuit work, I routinely took off with QFE set, and changed it QNH, or SPS, when I left the circuit.

I cannot quite see how taking off with QFE set would upset the A-10Cs IFFCC, but it just might explain why many of my group are getting consistent errors of 2-5 metres in delivering GBU-12s.

As a result, I will change the habits of a life-time (well, the last 55 years of it anyway), and henceforth use QNH for my take off.

Finding it very difficult to cope with all these new modern procedures - had enough problems when we switched from fixed undercarriages, never did me any harm - harrumph - harrumph!!!

RAF is weird to still be using QFE still. Almost no airplane operator does it the RAF (Soviet, Pan Am, Georgian) way anymore.

The A-10's INS has a sense of own altitude which it takes a snapshot calibration as the wheels reach a certain speed (50 knots or something) on the takeoff roll. That snapshot is then blended later by GPS updates.

DCS isn't modeled in enough detail for it to actually do anything and the real plane even miscalibrated wouldn't be off much (the blending might reduce a 1000' error down to 100' or something). In any case an LGB is a particular case in which the initial ballistic trajectory is divorced from the terminal accuracy as it's chasing the laser dot.

Don't know if they still do it because I didn't pay attention anymore, but at least until a few years ago British Airways pilots where the only ones who were always requesting the QFE at every airport.

Once again, the Brits doing things differently from the rest of the world. Somehow driving on the wrong side of the road wasn't enough... :D

Once again, the Brits doing things differently from the rest of the world. Somehow driving on the wrong side of the road wasn't enough... :D

How very dare you! I'll have you know that almost everyone used to 'drive' on the left and it was, in fact, you Frenchies (and the Americans who always have to be different :megalol:) that changed to the right! :lol: :book: https://www.worldstandards.eu/cars/driving-on-the-left/

And what's up with those Imperial units?? We're in the XXI century.. for crying out loud! :)

Looks like even the Russians are getting rid of QFE.

From February 2017, Russia is changing to use QNH and Feet below the Transition Level. The first airport to use this is ULLI/St. Petersburg.