QFE or Zero?

[VFE]

Hi folks,

An issue which has been bugging me somewhat of late is the setting of QFE when remaining in the circuit at an air/ground radio licensed airfield. I see some (usually older) instructors will instruct the student to set zero whilst on the ground prior to circuit work and others who will go with the recorded QFE setting as read by the airfield barometer and passed over the radio with it's oft inaccuracy when displayed on the altimeter of +/- 100ft or so...

Who is in the right?

Personally, I always advise setting the QFE (with possible error of +/- 100ft) as reported over the radio as that is what other aircraft arriving in the circuit will be using too, therefore we'll have more chance of being at the same height ergo better chance of spotting them, assuming their altimeter is correctly set and servicable that is!

I guess you could argue a reasonable case for 'zeroing' the altimeter too as that will give a closer accuracy to real 'height' above aerodrome however, in VFR it's not as safety critical in my view as an accuarate QFE due to above mentioned reasons of collision avoidance.

This lack of unity leads me to ask others here their methods and reasoning?

Many thanks,

VFE

[ScouseFlyer]

VFE

Surely given the situation you outline broadcast QFE should be used so as to give yourself the best opportunity of avoiding a mid-air in the circuit.Should have no real problems with height aal given the visual clues available.Unlicenced without a/g an entirely different matter.As my old instructor used to say its the one you don't see that gets you!

SF

[VFE]

Totally agree ScouseFlyer. Half the reason I posted this was to see if I've missed something which (and it does seem to be the case more often than not) the older more experienced instructors know and I don't...

VFE.

[Vortex Thing]

Many UK airfields have up to 60ft difference between threshold and the ARP so setting zero on the apron will not help much.

It also won't give you the correct separation from other traffic. If you are flying QFE or QNH it is not up to you to adjust as you see fit.

If you are flying from a strip or field that would be different but the datum are there for reasons greater than our own visual acuity. Do you really spend your last 50ft looking at the altimeter or looking out visually!

[bookworm]

Surely given the situation you outline broadcast QFE should be used so as to give yourself the best opportunity of avoiding a mid-air in the circuit.

How does everybody flying at exactly the same level give you a better chance of avoiding a mid-air?? Is it really that much harder to spot an aircraft 50 ft above or below? Isn't it actually a little easier?

[VFE]

Much harder to spot an aircraft a few feet below than above. I will freely admit that having anything set relies upon everyone maintaining level circuit height on accurate altimeters - bit of a long shot - but it's the inconsistancy amongst us instructors leading to unnecessary student confusion which bugs me (and the same awkward bloody question!).

How many times do you hear students remark "you instructors are all different you know!".

VFE.

[FlyingOfficerKite]

QFE where appropriate.

'Zero' is neither a setting nor a datum.

FOK :)

[Whopity]

We have an untrained man in a box setting zero on an uncalibrated altimeter and calling it QFE.

Then we have another man in an aeroplane with a supposedly calibrated altimeter at the end of the runway setting zero and calling that QFE!

Which is the most accurate QFE? Pure semantics!

Some of course wind on the aerodrome elevation and fly on QNH.

[SASless]

QFE, QNH, Zero set at any point, as a means to eliminate mid-air's in a traffic pattern?

What about covering up the altimeter....fly what looks right....and keep your Mark I's looking outside the windows as a means to traffic avoidance.

The key is arriving at a "height" above ground....and as no one is perfect in altitude control...altimeters have errors....and setting numbers maybe as much as an hour old.....or older....just what relevance does the altimeter reading have to do with traffic avoidance anyway?

You are only guessing at your height at the best of times anyway!

I would think flying a common track over the ground that is shared by all the other traffic in "the circuit" would go much farther in preventing a collision.

[ScouseFlyer]

The only point being made was that mechanical imperfections etc aside my experience is that it is easier to see an aeroplane at roughly the same height as yourself than one above or below you in a relatively tight piece of airspace such as a circuit even with mark one eyeball working overtime.

SF

[I Follow Roads]

If you are at an uncontrolled field with A/G service, and you are doing circuits, it is retarded to set a given QFE if it shows your aircraft being underground or 100ft up whilst still stationary! A transmitted QFE is a 'best effort' for pilots joining the circuit, especially at a lot of GA fields where it is derived from someone setting a ropey old aircraft altimeter (note - calibration for position error will be somewhat out of whack!) in the clubhouse - to ZERO.

As the legal requirement for altimeter accuracy is 2mb this gives the potential for 2 perfectly legal altimeters to be up to 120' out with each other! If everyone sets zero on the ground then everyone's altimeter will read circuit height at circuit height, and anyone joining on a transmitted QFE will be in the right ball park -ish. Anyone joining and then doing subsequent circuits would be best off setting zero on the first touch and go, presto! Everyone flying on EXACTLY the same reference - HEIGHT ABOVE FIELD ELEVATION.

As for the point about sloping airfields, most will employ a circuit altitude based on QNH anyway, for precisely that reason.

Of course if you're flying somewhere a bit more upmarket with ATC and decent equipment it's a different matter, and with a lot of my students I end up covering up the whole panel to stop them chasing the needles instead of flying the aeroplane!!

[LH2]

What about covering up the altimeter....fly what looks right....and keep your Mark I's looking outside the windows as a means to traffic avoidance.

That's actually how we do it in Alpine mountain flying, kind of: Fly level with some landmark (often someone's chalet :E) and set the altimeter accordingly... on QNH of course, unless you want to unwind six to ten thousand feet off it.