Learning to fly, or thinking of learning? Post your questions, comments and experiences here

Moderator: AndyR

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#1819531
T6Harvard wrote:I'd be very grateful if someone would clarify how I set the correct QFE as we return to the circuit.

The simplest way is to know the difference in hPa between the QFE & QNH at your airfield. Before starting the engine set the altimeter to 0', note the subscale reading. Then set the altimeter to the airfield elevation & again note the subscale reading. The difference betwen the two will always be the difference between QNH & QFE at your airfield.

So, get the ATIS QNH from East Midlands & then wind off the subscale by the number you remember from the QFE/QNH difference you noted earlier.
T6Harvard, cmoreflyer liked this
#1819533
I didn’t write that, but I agree with the others who responded: stick with QNH, mentally calculate the circuit elevation (if not given MSL on the plate) and join the circuit. Once I’m in the curcuit it’s more or less visual clues only, except to check that I turn final at no less than 500 ft AGL. After some more practice, you’ll be able to tell the difference between above or below 500 ft only by looking out. At least at familiar airfields. But, as has been said, check and check again.

We learned about QFE in my country, but I’ve never used it. Haven’t come across it anywhere except the UK, but I agree it looks handy when flying circuits only.

Happy training! :thumleft:
T6Harvard liked this
#1819535
I was always of the "QFE because I want the altimeter to read zero as I get to the ground" school of thought.
But this requires mental maths and as @T6Harvard says you need to remember when you've twiddled the knob. Much better to use QNH all the time and simply know the circuit altitude (ie airport amsl plus circuit agl).
And yes, you shouldn't be looking at the altimeter after you descend from circuit height - after that it's all judged on the picture, plus nailing the airspeed.
You should find, in fact, that your instructor will get you to do a whole circuit judged by eye without the altimeter at some point in your training.
T6Harvard liked this
#1819563
I consider manually winding the altimeter, without a specific setting, to have too much of a risk of getting it wrong. I'll only do it on the ground, setting it to zero or a known aerodrome elevation as appropriate. In the air, I won't ever adjust the altimeter except to a known setting.

I'm sure somebody's now going to tell me again which way to wind it. I know. I passed my theory exams which involved the necessary calculations and understanding. I can do it correctly. I still think it's too error prone to be worth doing.
#1819565
lobstaboy wrote:And yes, you shouldn't be looking at the altimeter after you descend from circuit height - after that it's all judged on the picture, plus nailing the airspeed.

I really do agree with this. The picture is everything, and learning it is a thousand times more useful than remembering stupid landmarks or heights at which to do things.
T6Harvard, malcolmfrost liked this
#1819568
rdfb wrote:I consider manually winding the altimeter, without a specific setting, to have too much of a risk of getting it wrong. I'll only do it on the ground, setting it to zero or a known aerodrome elevation as appropriate. In the air, I won't ever adjust the altimeter except to a known setting.

... which could have been misheard, or misremembered, or miswritten, or misread. I'm not sure winding off a height that you've planned is any less reliable.

This is an argument for knowing the circuit altitude, and flying QNH, which, although I don't do it myself, I think has a lot going for it.

I'm sure somebody's now going to tell me again which way to wind it. I know. I passed my theory exams which involved the necessary calculations and understanding. I can do it correctly. I still think it's too error prone to be worth doing.

There should be no calculation. Unless your airfield is below sea level, your height is always less than your altitude. So turn the knob so that the indicated height goes down by the airfield elevation. Watch the needle to make sure.
Rob P, T6Harvard liked this
#1819572
rdfb wrote:I consider manually winding the altimeter, without a specific setting, to have too much of a risk of getting it wrong.


I don't know about your panel but I have a big circular dial with a sweep hand for the hundreds of feet.

It's far easier to check that I have wound off the 190ft the Tibenham elevation correctly, both in terms of amount and direction, than ever it is to read the little subscale in a tiny window.

But we all have out own way of doing things, all that matters that we end up at the right height at the right time and place.

Rob P
#1819577
Rob P wrote:I don't know about your panel but I have a big circular dial with a sweep hand for the hundreds of feet.

It's far easier to check that I have wound off the 190ft the Tibenham elevation correctly, both in terms of amount and direction, than ever it is to read the little subscale in a tiny window.


What happens if you're winding off the height at Dunkeswell and mid change you hit a huge thermal? Eh? Eh? :D

Or worse still, at North Weald, where you have very little margin under Stansted's airspace.

It's nice to have the little window figures in such an eventuality, even if you do have old eyes...
#1819583
TopCat wrote:
rdfb wrote:I consider manually winding the altimeter, without a specific setting, to have too much of a risk of getting it wrong. I'll only do it on the ground, setting it to zero or a known aerodrome elevation as appropriate. In the air, I won't ever adjust the altimeter except to a known setting.

... which could have been misheard, or misremembered, or miswritten, or misread. I'm not sure winding off a height that you've planned is any less reliable.


Ways in which winding an altimeter could go wrong:

  1. You wind it the wrong way by accident.
  2. You wind it twice because you were already on the QFE (eg. you did some circuits before departing so you were on the QFE and forgot to set it to a QNH).
  3. You forgot to ensure you were flying straight and level before you started to wind it.
  4. You weren't trimmed well so you didn't hold straight and level while you wound it.
  5. You mishear, misremember, miswrite or misread the aerodrome elevation.
  6. You get your arithmetic wrong (eg. altitude 2300 feet minus aerodrome elevation of 145 feet = ???)
  7. You misread the scale (eg. move it 800 feet instead of 80 feet).

You might think that the above won't happen to you. But mistakes usually happen when there's something else not going to plan, and you follow habit even though it's no longer appropriate because of what has changed (yet due to high workload, you are unable to identify that you need to adjust your habit, or what you need to do differently this time).

Not that setting QFE is so important when flying VFR, because as others have said, I don't look at it when below circuit height except for flaps/turn on climbout. But if I do an instrument approach I'll do it on the QNH for this reason, and have my DA/MDA written down in front of me as well as set on the altimeter bug. So I prefer not to be in the habit of winding the altimeter.

The QNH could indeed be misheard, or misremembered, or misread, but that's only one thing. Your method to get the QFE will add to any QNH mis-setting error, since you'll likely have received QNH updates enroute. Also, if you stick to the QNH, you'll generally only hear one or two hPa difference every time; if you hear a big change you can be in the habit of confirming it. That provides some protection against gross errors.
T6Harvard liked this
#1819610
I've got it wrong.

On a flight to a strip I'd never been into before, delivering the aeroplane for maintenance. I'd written circuit altitude down as 1100ft in my plan. height (800) + elevation (300), ready for QNH. In flight a few things went a bit wrong, vis wasn't good, I was running out of daylight and a comms problem with the neighbouring airport who's airspace I was in, was all adding to the workload, along with only 1hr flying in the previous 3 months.

Airfield in sight, and I can join directly on downwind, in my head I then added 300ft to the circuit height and flew into the circuit at 1400ft. Turned base, then final at 1200ft, then realised what I'd done. "Bugger! I'm not going round". Full flap, side slip. Over the fence a bit high and fast. Lots of the 450 mtrs soon disappears! Left the go-around decision too late, trees to clear. Finally got the slick tyres onto the wet grass, and she slid, and slid.... Gentle dabbing of the brakes stopped me just short enough of the fence so that I could still turn around to back track!

Whilst the whole flight was one full of errors (all mine), QFE, would have prevented the workload induced one that nearly bent the aeroplane.
mick w, T6Harvard, Rob P liked this
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