Primarily for general aviation discussion, but other aviation topics are also welcome.
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When doing circuits, what height setting do you use on your altimeter?

QFE
128
65%
QNH
66
33%
RPS
No votes
0%
I don't look at the altimeter anyway
4
2%
User avatar
By Dave_Ett
#1519052
kanga wrote:.. and it relies on external signals and internal power, either of which could fail at any time. If barometric altimeter is working at start of flight, set to whatever subscale value pilot chooses to use, there is a pretty good chance it will keep working adequately throughout any sort of flight which I would undertake. :)


External signals are beyond improbably to fail. GPS is now too necessary that the US will never turn it off. Maybe.

Is the likelihood of people getting their altimeter settings mixed up, or their maths wrong higher or lower than power failing these days? Given that many people (most?) fly with a battery powered navigation device as well as an aircraft power source, I very much doubt that the loss of both will occur with any regularity.

Modern civil airliners have to have an emergency electrical system available for 10^-9 of the flying time. 1 failure every thousand million hours (I think!).
User avatar
By T67M
#1519053
GPS last failed on Jan 26th 2016. Worldwide. For nearly 24 hours. Fortunately the position element wasn't affected on this occasion - but position errors have happened to GNSS in the last few years with a 40km error.
Last edited by T67M on Mon Feb 13, 2017 4:50 pm, edited 1 time in total.
By James33
#1519054
QFE not used at all over here, although all airfield charts indicate circuit height with both QNH and QFE.

Of course, in order to have the local QNH you need to be speaking to somebody, and I know some pilots have a very "radio light" approach to flying, so I can understand how being passed the QFE could be useful.
User avatar
By kanga
#1519056
johnm wrote:"Keep It Simple Stupid" was always good advice and a nice basic barometer showing altitude above sea level is as simple and effective as it gets in this context.


I recall a tale in one of the Alastair Cooke Letters from America. Someone in New England took a parcel to the local small rural Post Office. He explained to the clerk that he was returning a mail-order barometer because it was obviously faulty, as the pointer was stuck on Hurricane. While he was at the counter the hurricane struck ..
User avatar
By Dave W
#1519059
T67M wrote:GPS last failed on Jan 26th 2016. Worldwide. For nearly 24 hours. Fortunately the position element wasn't affected on this occasion - but position errors have happened to GNSS in the last few years with a 40km error.


Ah, but when was the last time somebody's GPS batteries ran flat?
#1519061
James33 wrote:Of course, in order to have the local QNH you need to be speaking to somebody, and I know some pilots have a very "radio light" approach to flying, so I can understand how being passed the QFE could be useful.


:?:

If you wind in the field elevation on your altimeter before you go, you will have the QNH and unless you fly for very long or very far that QNH will be good for a fair while, innit?
johnm, flyingeeza liked this
#1519087
Dave_Ett wrote:.....switch to using GPS based....we only need vertical information to stop us flying into each other...

Speaking of which...
Have y'all heard about the latest must-have gizmo called PilotAware?

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kanga, Dave_Ett liked this
By Joe Dell
#1519155
Flyin'Dutch' wrote:
Joe Dell wrote:Referring to the OP. Why would I want to go down the airfield (UK) and fly circuits on anything other than QFE?
Can anyone give me one good reason not to? Where's the advantage in sitting on the ground and winding my altimeter up from zero to airfield elevation?


- Flying using the QNH allows you to gross error check the function of your altimeter before you get going;
- Flying using the QNH gives you relevant information in relation to obstacles, terrain and airspace around you;
- Flying using the QNH equips you with the correct information when you are flying to other airfields and avoids the need to change altimeter settings unnecessarily - you just read the circuit altitude from the plate;
- Flying using the QNH prepares you to fly to/from airfields which are higher than the sub scale lets you wind off;
- Flying using the QNH prepares you to fly abroad and to airfields where a QFE may not be available (either by convention or because there is nobody who can give you the QFE over the radio);
- Flying using the QNH prepares you for the day that you decide to continue your training and development and either go and fly on instruments in IMC or strip flying where the QNH is a lot more useful to have than a QFE from an airfield you are not going back to;
- Flying using the QNH makes you more weather aware.

Other than that I can not see any advantage of using the QNH over the QFE.

:twisted:


I'm surprised that you managed to read my post without understanding a word of it. :(

Fast forward and have a careful listen here between 14 and 16 minutes in.
#1519172
For me the biggest reason for using QNH all the time is it minimises the chance of setting it wrong. If you set the airfield elevation when all is nice and quiet and stress free, in the vast majority of cases for GA flying in the UK it will be accurate enough, or maybe only need a tweak by the odd HPa or so. (Unless you fly flight levels of course.
I have misset my altimeter by 10HPa joining the circuit and it is very easy to do.
#1519173
Flyin'Dutch' wrote:- Flying using the QNH allows you to gross error check the function of your altimeter before you get going;

Why is that different from QFE then? I was taught to zero the altimeter, add 10mb and check display, then back to zero. Wind off 10mb, check display and then set to QFE / QNH as required.

Flyin'Dutch' wrote:- Flying using the QNH gives you relevant information in relation to obstacles, terrain and airspace around you


The thread is about QFE in the circuit. Don't think anyone is arguing against QNH outside the circuit!?

Flyin'Dutch' wrote:- Flying using the QNH prepares you to fly to/from airfields which are higher than the sub scale lets you wind off


Can you explain this please? ( Yes I know I'm ignoring the point of the thread - QFE in the circuit)

Flyin'Dutch' wrote:- Flying using the QNH prepares you for the day that you decide to continue your training and development and either go and fly on instruments in IMC or strip flying where the QNH is a lot more useful to have than a QFE from an airfield you are not going back to;


What's the reason QFE isn't used when on instrument approach? I would have expected an FD or AP to want to know when touchdown was imminent by knowing 0 feet = runway. (Again ignoring the point of the thread - QFE in the circuit)

Flyin'Dutch' wrote:- Flying using the QNH makes you more weather aware.


How does it help more than QFE in the circuit?
mick w liked this
By johnm
#1519174
Well I did as asked but don't see what the point was.

They were given the QFE and set it, they checked it on approach (very good). They could have got both QNH and QFE from the ATIS used QNH and checked field elevation, they then had the choice of a visual or instrument approach with no further action needed.

A student was given the QNH on taxi request as they were on final as it happens. Having both just adds a potential confusion and hazard as far as I can see.
User avatar
By flyingeeza
#1519195
johnm wrote:Well I did as asked but don't see what the point was.

A student was given the QNH on taxi request as they were on final as it happens. Having both just adds a potential confusion and hazard as far as I can see.

Agree...no point, except...
What I did learn from that video is where to stick my multitude of GoPro cameras to maximise their detrimental effect on my lookout. :D

Dave_Ett might find that this answers one of his questions...
look at the altimeter as they land...it's reading around 40 feet low despite all the hype about QFE being so important near the runway. It read zero while they were on short final at what looked to be at least 30 to 40 feet over the threshold anyway.


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