91.205 compass requirement

maanantai 18. huhtikuuta 2016 17.19.06 UTC+3 Jonathan St. Cloud kirjoitti:
My ASG-29 POH requires one magnetic compass. I tried to use a little $4 stick on commas, but the examiner would not license it without a "robust aviation compass". So I had to mount one on the glare shield. I have two electronic flux gate compasses, plus maps and eyes so I thought I could leave the whiskey compass, not so


What would examiner think of magnetic compass sensor built into variometer? I ditched my compass after installing AIR Glide with compass sensor.

On Wednesday, April 20, 2016 at 3:50:47 AM UTC-7, wrote:
Ah indeed you are right, and this exact point with 91.205 has come up on r.a.s. before, and as pointed out here in the past by others AC-21.17-2A precisely covers this.

http://www.faa.gov/documentlibrary/m...c_21.17-2a.pdf

Directly from that AC:

"Section 91.205 of the FAR. Powered gliders are considered to be powered aircraft for the purpose of complying with § 91.205 "

So to your point, except there is no flexibility here with no difference between a retracting engine self-launcher and touring motorglider etc. (and note as made very clear in this AC sustainers are also "powered gliders").


Thanks Daryl, I now see this has been discussed on RAS before, as you said. I had not seen the past discussions. I should have done a search for past discussions of this topic. The AC you point out is clear for motorgliders on the 21.205 compass question we are discussing.

However I note that the AC preamble says "this material is neither mandatory or regulatory in nature, and does not constitute a regulation". I assume that means the AC's guidance on 21.205 is open to a different conclusion? I think its arguable that the AC's guidance on 21.205 is inconsistent with the FAA definition of a glider as "a heavier than air aircraft, that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and its free flight does not depend principally on an engine". This definition logically explains the otherwise-strange FAA view that a motorglider is a glider (even a touring motorglider). But following that definition, ie assuming motorglider free flight 'does not depend principally on an engine', a motorglider should more logically not be considered a 'powered aircraft' for 21.205.

That is required verbiage because legally the AC is not making a regulation.... in practice this tells you exactly how the FAA sees this. It's nice to have that AC as it does fix lots of questions that would otherwise exist.

Very recently a A&P/AI told me his recent experience with FSDO inspector required a compass correction card in a 2-32 that had no compass and no requirement for one in the MEL or POH. He didn't need the compass just a correction card, he then signed off the glider and issued the new airworthiness certificate. So figure that every FSDO and every inspector within are interpreting the FAR's differently. Your results may vary

I know this discussion is very US centric, but I thought some may like to know that in Canada too there is often confusion about the need for a magnetic compass. However, the CARS (regulations) are clear that a glider needs only an airspeed indicator and an altimeter. They do, however, specify that a powered glider must also have a magnetic compass. Further, any glider with the ability to carry water ballast must also have an outside air temperature guage.

Also interesting is the confusion about the need for a compass correction card. Everyone thinks it is necessary yet the regs here say that it is only necessary if the compass is off by at least 5 degrees at any point. Quite sensible, I would think, and it is far better than our AME's simply making up some numbers on a card as is often the case (rather than doing a proper compass swing.) It is amazing how something that should be quite clear results in so much confusion among people in the industry.

ALL gliders in Canada are required to carry a compass or magnetic direction indicator - it's easy to get confused because the CARS airworthiness requirements specify just an altimeter and ASI for a pure glider (plus OAT if water ballast is available and an accelerometer if in category A) and only require a magnetic direction indicator in powered gliders (522.1303) BUT under General Operating And Flight Rules we find:

"Gliders -- Day VFR

605.21 No person shall operate a glider in day VFR flight unless it is equipped with

(a) an altimeter;

(b) an airspeed indicator;

(c) a magnetic compass or a magnetic direction indicator; and

(d) subject to subsections 601.08(2) and 601.09(2), a radiocommunication system adequate to permit two-way communication on the appropriate frequency when the glider is operated within

(i) Class C or Class D airspace,

(ii) an MF area, unless the aircraft is operated pursuant to subsection 602.97(3), or

(iii) the ADIZ."

So, yes you are required to have a compass. I too had a brief moment of hope that I could throw the compass away when I read the airworthiness requirements part of the CARS only to be disappointed when I read the operating and flight rules.

The point about the fact a correction card is not required if the deviation is less than 5 degrees on all headings is correct. Not well known though.