Cessna 172S POH wrong!
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Cessna 172S POH wrong!
Been doing some weight and balance on a Cessna 172S recently and have come across a (very) worrying problem. On Page 6-15 and 6-16 of the POH there are the figures for Centre of Gravity Moment Envelope and Center of Gravity Limits. Important stuff I'm sure you'll all agree!
I'm planning in metric here in Australia and using the Kilogram scale on the right of each chart. Could't get three adults and full fuel to work the other day, so checked the calcs in lbs and not Kgs; this time it worked!!
Looking at figure 6.7 and 6.8 there is clealry an error in the kg/lbs conversion; one of the scales is wrong! The revision number in the POH is May 30/00.
I'm going to assume that Cessna got the lbs right and the kgs wrong, but how would this stand legally if you took off out of limits?
I'm planning in metric here in Australia and using the Kilogram scale on the right of each chart. Could't get three adults and full fuel to work the other day, so checked the calcs in lbs and not Kgs; this time it worked!!
Looking at figure 6.7 and 6.8 there is clealry an error in the kg/lbs conversion; one of the scales is wrong! The revision number in the POH is May 30/00.
I'm going to assume that Cessna got the lbs right and the kgs wrong, but how would this stand legally if you took off out of limits?
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Check the aircraft w&b . I am a bit worried if you have three big guys and full fuel you will be out , 3 middle weight guys maybe or two guys and a small woman will work
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"AFM" is the formal regulatory term for the document which contains the authoritative information/limitations, by which the aircraft must be operated. "POH" was often the term used by Cessna, and there was a statement in the front stating that the POH was the document by which the aircraft was to be operated, as there was no more formal equivilent.
Though the POH or AFM might contain sections whoch are referred to as "unapproved", that's a regulatory thing, and it does not mean that the referenced information is not the most authoritative. A manual for an aircraft which contains pages marked "unapproved" is a sure sign that other pages in that document are approved.
Though errors can, on rare occasions, be found, these documents are very carefully worded as to their authority.
Though the POH or AFM might contain sections whoch are referred to as "unapproved", that's a regulatory thing, and it does not mean that the referenced information is not the most authoritative. A manual for an aircraft which contains pages marked "unapproved" is a sure sign that other pages in that document are approved.
Though errors can, on rare occasions, be found, these documents are very carefully worded as to their authority.
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No matter how long the runway, getting airborne with the C of G beyond limits is still a very bad idea! Sometimes the shorter runway is safer, it makes it more clear that the attempt to fly is not working as it should, and a rethink is necessary!
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POH Error ?
WOW ! I am amazed this error has not been pointed out before. 
My 172S "Information Manual" p/n 172SIM dated 30 May 2000 has, indeed, the same kg to lbs error on the figures you referenced. I've checked my other Info Manuals for the 172R and they're correct, at least back to 1986, and have found no similar errors in my collection of 182 manuals.
Nice catch ! (Yes, I believe the Cessna "pounds" scale is correct as you mention, but they goofed up the kg conversion).
BTW, Cessna singles came with an unofficial "Owner's Manual" until 1976, when they adopted the GAMA formatted "Pilot's Operating Handbook" (POH) - then, in 1979, the FAA Approved "Pilot's Operating Handbook and Airplane Flight Manual" (AFM) became required equipment. The "Information Manual" was introduced then as a duplicate of the AFM, but not approved as a direct replacement for the actual AFM.
I'm going to cross-post this at the Cessna Pilots Association to make sure everyone is aware.
Again, NICE CATCH ! Since it obviously affects an FAA Approved AFM, there really should be an Airworthiness Directive (AD) issued to point out the problem (even though I'm not a fan of excess regulation, W&B issues ARE important.
Cheers.
My 172S "Information Manual" p/n 172SIM dated 30 May 2000 has, indeed, the same kg to lbs error on the figures you referenced. I've checked my other Info Manuals for the 172R and they're correct, at least back to 1986, and have found no similar errors in my collection of 182 manuals.
Nice catch ! (Yes, I believe the Cessna "pounds" scale is correct as you mention, but they goofed up the kg conversion).
BTW, Cessna singles came with an unofficial "Owner's Manual" until 1976, when they adopted the GAMA formatted "Pilot's Operating Handbook" (POH) - then, in 1979, the FAA Approved "Pilot's Operating Handbook and Airplane Flight Manual" (AFM) became required equipment. The "Information Manual" was introduced then as a duplicate of the AFM, but not approved as a direct replacement for the actual AFM.
I'm going to cross-post this at the Cessna Pilots Association to make sure everyone is aware.
Again, NICE CATCH ! Since it obviously affects an FAA Approved AFM, there really should be an Airworthiness Directive (AD) issued to point out the problem (even though I'm not a fan of excess regulation, W&B issues ARE important.
Cheers.
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Hmmmmm... I would have thought this was common knowledge for anyone who flies a C172S in the kg world?
I know I was informed of it when I started flying the 172S, and was told it was something "everybody knows and nobody fixes". The POH's I have seen for the 172S have had a pencilled note not to use the kg scale.
But it is indeed worrying if there are people who still aren't told, so spreading the word is probably a good idea.
I know I was informed of it when I started flying the 172S, and was told it was something "everybody knows and nobody fixes". The POH's I have seen for the 172S have had a pencilled note not to use the kg scale.
But it is indeed worrying if there are people who still aren't told, so spreading the word is probably a good idea.
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Bjørn, most of my flight time is in 182s and Mooney's, so I must have missed the 172 "common knowledge" you mention - it still strikes me that depending on penciled notes in the absence of at least a Cessna Service Bulletin or AD is not appropriate given common trust vested in an AFM.
Anyone know if there is such a document?
Cheers,
Trolltuner
Anyone know if there is such a document?
Cheers,
Trolltuner
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What troubles me is that it is not a new find, it has been pointed out many times before, and it is still not corrected, or at least not corrected everywhere. Pencilled notes and word of mouth is of course not the right way to make the information known.
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I'm with you all on this one. It was a new find for me; but as Bjornhall points out, I'd much rather it had been corrected in the POH of the acft I rented before I and my fellow pilot had to work it out!
Surely the structure of the POH is such that it allows for page revisions (like Bottlang etc) so have cesna owners not been contacted and provided with an updated table? Maybe they have?
In the meantime, if we assume (dangerous) that the imperial lbs scale is correct at least the metric error is in favour of a more conservative approach i.e. it creates an over MTOW when in fact the imperial scale indicates a 'within envelope' situation.
Any views from 172s owners rather than renters, like me?
Surely the structure of the POH is such that it allows for page revisions (like Bottlang etc) so have cesna owners not been contacted and provided with an updated table? Maybe they have?
In the meantime, if we assume (dangerous) that the imperial lbs scale is correct at least the metric error is in favour of a more conservative approach i.e. it creates an over MTOW when in fact the imperial scale indicates a 'within envelope' situation.
Any views from 172s owners rather than renters, like me?
Glad I found this guys. Thought I was going mad and couldn't work out where my 50kg got lost. Eventually realised that if I shot across from 2200lb I didn't hit 1000 kg ! As an update the latest POH for the G1000 172S (rev 4 2006 doc no 172SPHAUS-04) has it corrected.
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If this has been common knowledge for so long why haven't Cessna corrected it? Doesn't fill you with confidence does it. I work in pounds so it doesn't really affect me but it makes you wonder what other errors there are in there (and indeed in other POH's).
The whole area of weight and balance and performance charts is a bit of a 'plus and minus 20%' game to me. (Yes I'm aware of the CAA performance multipliers.)
The whole area of weight and balance and performance charts is a bit of a 'plus and minus 20%' game to me. (Yes I'm aware of the CAA performance multipliers.)
Andy P
It is the operators responsibility to keep the POH up to date. Cessna fixed this problem in the 2006 revision so you should be asking the owner/operator of the aircraft why he she is not keeping the POH up.
It is the operators responsibility to keep the POH up to date. Cessna fixed this problem in the 2006 revision so you should be asking the owner/operator of the aircraft why he she is not keeping the POH up.
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Very interesting!
I just checked the POHs of the two a/c I fly most, a 172RG (1983) and a 182RG (1979). In both cases the kilo > pound ratio is correct.
In any case - three guys and full fuel in any SEP is going to be marginal unless this is a group of jockeys flying to their next race!
I just checked the POHs of the two a/c I fly most, a 172RG (1983) and a 182RG (1979). In both cases the kilo > pound ratio is correct.
In any case - three guys and full fuel in any SEP is going to be marginal unless this is a group of jockeys flying to their next race!