IFR Altimeter Error

[dogcharlietree]

Am I being pedantic?
Jepps - ATC, AU-501 Section 1.1.2 IFR Altimeters.
Para 1.1.2.1 "With an accurate QNH set, the altimeter(s) should read the nominated elevation to within 60ft. If an altimeter has an error in excess of +/- 75ft the altimeter is to be considered unserviceable."
NB Bold is my emphasis.

My concern is the (mis)use of the word "ERROR". It has a tolerance, which is not the same as an error.
ie according to that paragraph quoted, if the altimeter reads within +/- 135ft, then it is serviceable.
To put it plainly, if the altimeter read 61ft, it would have an error of 1ft.
I would presume that what the authority meant was, if it reads within +/-75ft (ie an error of 15ft), it is still considered to be serviceable, but out of required tolerance.

Ok, I will now put on my flak jacket.

This would be better wording;
"If an altimeter reads in excess of "+/- 75 ft from the nominated elevation", the altimeter is to be considered unserviceable." :D

[harrowing]

I agree with your interpretation. That is probably what was meant.
Perhaps this will help any further queries.
Courtesy of www.dicksmithflyer.com.au
Cheers :ugh::confused:

Proposed Civil Aviation Regulation Act

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Rule 1000(b). If the pilot or group of associated pilots become aware of, or realises, or detects, or discovers, or finds that he, or she, or they, are, or have been, beginning to understand the Civil Aviation Regulations, they must immediately within three (3) days notify in writing the Director.



Rule 1000(c). Upon receipt of the abovementioned notice of impending comprehension, the Director will immediately re-write the Civil Aviation Regulations in such a manner as to eliminate any further comprehension hazards.



Rule 1000(d). The Director may, at his or her option, require the offending pilot, or pilots, to attend remedial instruction in the Civil Aviation Regulations until such time that the pilot, or pilots, are too confused to be capable of understanding anything

[capt787]

assuming elev = 1000ft, if your ALT read 1015ft, your ALT ERROR = +15ft, which is serviceable

if you read 1065ft, your ALT ERROR = +65ft, NOT +5ft

if you read 950ft, your ALT ERROR = -50ft

ALT ERROR = the diff btw your ALT reading and elev.

[Jabawocky]

Geeeez...... an error of 50 feet at the correct QNH......... Bin the it quick!

J

[Short_Circuit]

It can have an error and still be with-in tolerance.


The eg. has an error of 60 ft ((QNH + 60)not indicating correct Alt, out by 60ft) but is with-in tolerance.

The indicator is in error.

The statement is true.

[Chimbu chuckles]

Where did you get +/-135' from?

It is really pretty simple.

With an accurate QNH set the altimeter should read elevation. The only accurate QNH would be station QNH from AWIS/ATIS/TWR...not area QNH.

So if the elevation was 500' and the altimeter read between 425' and 575' (500' +/-75') it would be considered serviceable and you're good to go. Even if it is outside that tolerance you're in fact good to go and check at the next airport.

[MajorLemond]

this is a bit ridiculus, lets face it: aviation as it is has way to many rules and regulations, and we don`t need to sit here all pick pointless s@#t apart for no good reason, :=

how the hell is "error" misused ? if the charted elevation is 20ft, with accurate QNH an altimeter reads 40ft, it is 20ft in ERROR. Really simple.

If you read your jepps and you get confused when you read that sentence you need help.

Don`t make it harder than it needs to be :)

[training wheels]

I think you'll find that if you referred to the regulation as a whole, then it makes a lot more sense. What you've quoted is only one of four sub-paragraphs from the AIP relating to IFR altimeter serviceability.

From the AIP, it basically says;

1. If your altimeter reads within +-60 ft of aerodrome elevation, then you're good to go.

2. If it reads between 60 ft and 75 ft, then you can fly to another point to get it checked (or serviced).

3. If it reads more than +-75, then it's unserviceable and you need to fix it before you can depart and operate under IFR. (ie, you can't fly to a another point to check it; you need to fix it at your current aerodrome.)

4. After flying to the second point (with an error of not more than +-75ft), you find that the altimeter still does not read within 60 ft, then it's US and you need to fix it.

Well, that's the gist of it. Here's the relevant section of the AIP. Read it as a whole and it makes more sense. :ok:

ENR 1.7 ALTIMETER SETTING PROCEDURES

1. PRE-FLIGHT ALTIMETER CHECK

1.2 IFR Altimeters
1.2.1 With an accurate QNH set, the altimeter(s) should read the nominated elevation to within 60FT. If an altimeter has an error in excess of ± 75FT, the altimeter must be considered unserviceable.

1.2.2 When two altimeters are required for the category of operation, one of the altimeters must read the nominated elevation to within 60FT. When the remaining altimeter has an error between 60FT and 75FT, flight under the IFR to the first point of landing, where the accuracy of the altimeter can be re-checked, is approved. In the event that the altimeter shows an error in excess of 60FT on the second check, the altimeter must be considered unserviceable for flight under the IFR.

1.2.3 An aircraft fitted with two altimeters but requiring only one for the category of operation may continue to operate under the IFR provided one altimeter reads the nominated elevation to within 60FT. Should the remaining altimeter have an error in excess of 75FT that altimeter must be placarded unserviceable and the maintenance release appropriately endorsed.

1.2.4 When an aircraft is fitted with only one altimeter and that altimeter has an error between 60FT and 75FT, flight under the IFR to the first point of landing, where the accuracy of the altimeter can be re-checked, is approved. In the event that the altimeter shows an error in excess of 60FT on the second check the altimeter is to be considered unserviceable for flight under the IFR.

[dogcharlietree]

Ok guys. Let me make it a bit simpler (however one or two have picked up on what I was trying to get at).

When is an ERROR not an ERROR??? Yes, I'm trying to interpret the WORDING, not the INTENT.
If it reads 59ft, it is acceptable, therefore, presumably it is within tolerance, NOT in error!
The para quoted states "If an altimeter has an error in excess of +/- 75ft the altimeter is to be considered unserviceable."

Please try and read what I've written, not what you think I wrote. :=
Remember RTFQ :ugh:

[training wheels]

The para quoted states "If an altimeter has an error in excess of +/- 75ft the altimeter is to be considered unserviceable."

Please try and read what I've written, not what you think I wrote. :=
Remember RTFQ :ugh:

I've read your FQ and there is no ambiguity if you read the regulation as a whole. That's my answer. If you don't like what you hear, then tough. :ugh:

[Dogimed]

Abbreviated

"Two things displease me. The extra fifty feet above the five thousand is sloppy flying and there is too much light in the cockpit.......
.....I rotate it forward an inch or so, then pull back the two red-topped throttles a like amount. At once a subtle change occurs within the cockpit.....

...The altimeter needle indicates precisely five thousand feet....

..., he bends forward and starts to adjust his tie. This humble gesture is almost the very last the human body identified at Beattie will ever be called upon to make.
For his next movement is a parting of the lips, followed by a horrible, inarticulate sucking sound, audible even above the engines. His actual cry of instantaneous shock is still unfinished when my own attention is drawn to the windshield. My every sense is appalled. There is not time-space for true fear to build, but the primeval urges are instantly uncovered. My stunned brain demans a challenging scream yet I am unable to make any sound. My body, along with my soul, has stopped dead, severed of all vitality within.
My hands freeze on the control wheel. In the blackness ahead there is a sudden, hideous apparition; the mass is no more than a thickening of the night, but it supports a green wing-tip light and, just below it, two flickering tongues of engine exhaust flame.......
....The entire drama begins and ends in two seconds. Beattie and I are sole members of the audience, for it is obvious that those in the other airplane never saw us.

Yet, except for a miraculous separation of no more than fifty feet, they would also be quite dead. Only a new audience on the ground would have heard the explosion. And watched the descent of two bundles of flaming metal."

- Ernest K Gann "Fate is the Hunter"

Apologies for the thread drift.

Dog

[BrokenConrod]

For those who think 50ft is nothing... Lets hope you learn.
Abbreviated

"Two things displease me. The extra fifty feet above the five thousand is sloppy flying and there is too much light in the cockpit.......

....The entire drama begins and ends in two seconds. Beattie and I are sole members of the audience, for it is obvious that those in the other airplane never saw us. Yet, except for a miraculous separation of no more than fifty feet, they would also be quite dead. Only a new audience on the ground would have heard the explosion. And watched the descent of two bundles of flaming metal." - Ernest K Gann "Fate is the Hunter"

What absolute drivel!

BC :}

[Jabawocky]

dogcharlietree (http://www.pprune.org/forums/member.php?u=57623)

When is an ERROR not an ERROR??? Yes, I'm trying to interpret the WORDING, not the INTENT.
If it reads 59ft, it is acceptable, therefore, presumably it is within tolerance, NOT in error!


I read that to mean..... The error is 59 feet. It is an error, pure and simple, however it may be an ACCEPTABLE ERROR.

J:ok:

[dogcharlietree]

What absolute drivel!

BC

My Dear BC. To make a statement like that when quoting "Fate is the Hunter", means you are either very young or very naive. There are lessons in there that may one day (or night) keep you out of the ground and you won't find them in any CASA sanctioned textbook.
When you decipher my username, you may know what I mean.

[Jabawocky]

You flew a DC3:ok:

And your altimeter was Rat$hit :}

J

[dogcharlietree]

I'm impressed!!!:ok:

[BrokenConrod]

you are either very young or very naive

Yep, that's me! I learnt most of what I know from reading a copy of Jonathan Livingstone Seagull that my grandad gave to me for my 10th birthday!

BC :}

PS: The extra fifty feet above the five thousand is sloppy flying
True, but it is pure chance that the other party was not at 5020' rather than 5070 or whatever' !!!! Precise flying had nothing to do with the outcome - just pure chance!

[dogcharlietree]

Yep, that's me !!!!! I learnt most of what I know from reading a copy of Jonathan Livingstone Seagull that my grandad gave to me for my 10th birthday!

Then may I suggest "A Gift of Wings" by the same author. Another excellent book.

[Dogimed]

True, but it is pure chance that the other party was not at 5020' rather than 5070 or whatever' !!!! Precise flying had nothing to do with the outcome - just pure chance


RIP Airmanship I guess eh?

Dog