Why ignore the POH?

[DX Wombat]

Why is it that, as far as I can see, every time someone asks a question or for advice, about the operation of an aircraft, most people simply jump in with their own favourite method, list, etc? Surely when a specific question is asked the correct thing to do is point the enquirer in the direction of the POH? The AAIB is likely to take a dim view of things if Joe Bloggs says he or she didn't follow the manufacturer's recommendation but decided to use Fred Smith's ideas instead. Not only that, if the correct procedure isn't followed can you be sure the Insurance company would pay out? Would you be happy if someone was killed or injured because they followed your advice if it was different from what the manufacturer recommended?

[moggiee]

Originally Posted by G-EMMA

Do you know what the role of the AAIB is BTW? I don't think it is in their remit to take a view on or judge anything unless that has changed recently? (sorry I'm being rude again - more myths)

It IS in their remit to determine cause, and if that involves pointing of fingers, then they will do that. For example, if the crash was caused because a pilot did not lower the landing gear, then they will say so - and you can argue that this is both "determining cause" and "judging".

It is then up to the CAA to decide if a prosecution is in order.

There is a lot of info in a POH and many people find it all too confusing - far easier to ask "Fred from the club". Too few schools insist that students answer these questions by finding the answers - yet if you are helped to find the information in the POH for yourself you will then a) be more likely to remember it in future or b) know where to find it next time you forget!

[moggiee]

G-EMMA - that's just semantics. They don't say "Captain so and so cocked it up" but the reports EFFECTIVELY point the finger by telling you what happened. As their job involves "determining cause" and 80% of causes are people, then that "points the finger" by default.

What happened and who/what caused it to happen are inextricably linked.

For example, the AAIB tells us that the crew of the Kegworth 737 closed down the wrong engine and pointed out the failings in their actions and those of the CAA, Boeing, BMA (as was then) et al. This is not direct "finger pointing", but by pointing out WHAT went wrong, they also tell us WHO was responsible.

Anyway, that's digression. The facts of life are that many, many people will take what "Fred at the club" says as gospel because they can't be asked to look it up for themselves. In the RAF we called it the "standard crewroom error" - in that one self-appointed authority would take it upon himself to tell everyone else how he thought it worked and you all ended up believing his version.

OK, so the POH doesn't have all the answers - but no book does. POH, Checklist, AIP, FIH, ANO, LASORs etc etc. when all pulled together have the answers. It may take a while but you can always find the answer written somewhere.

Of course, if the instructor doesn't know where to find it, he can't tell the pupil!

[fireflybob]

To return to the original question I think the answer lies in basic training - how many students are shown the POH/Aircraft Flight Manual? With some organisations it's not even freely available for reference.

[Rod1]

“if you can find me one published report that in any way points the finger I will change my view.”

Have a look at the G-STYX report.( It has since been shown the repair was not responsible for the accident.)

The POH in most aircraft are 40 years old. I have seen POH which specified “do not lean below 3000 ft”. Times change, fuel becomes very expensive. The engine manufacturers change the operating procedures for your engine. What do you do now, follow the Engine manufacturers advice on how to operate the engine, or the airframe manufacturers 40 year old advice. There is no “right” answer, understand the context and make an informed choice.

Rod1

[The Flying Pram]

I'm sure I have read many times that POH figures are derived from the performance of a brand new Aircraft in tip top condition. So basing your take off distance, for example, on these figures is likely to give you a false sense of security when dealing with a typical 30 year old flying school "hack". This could be why many pilots rely on their own judgment, or that of an instructor,
when faced with such a situation.

[SkyCamMK]

Yep Flying pram, that can make a big difference and older aircraft have written down values for use in CAA approved flight tests for ROC for example. When CAA FU approved checklists that I have produced in the past as part of an aircraft approval for flight tests and cpl/ir training the items they were concerned about were: to make sure that the emergency procedures were identical to the ones in the POH. Otherwise one SEP checklist is much the same as any other with a few slightly different V speeds, and pther diffferences re complex items such as VP props and retractable gear. IMHO there is no "one big book" to fly by as for many situations the variables are many and varied even in POH there are options printed for use with floats, autopilot etc that are not always fitted. That is not to say that CofA items can be disregarded.

[smith]

The performance data for the POH, as well as being carried out in a brand new tip top aircraft, is also carried out by a tip top test pilot as well, who no doubt can handle x/w landings etc like riding a bike.

[bjornhall]

Still, with the proper safety factors added, it is the best data we've got...

I am trying to recall accidents where the POH data said it would be ok but it wasn't; seems to be pretty rare isn't it? In the majority of overruns and collisions with obstacles, even the POH showed that it wouldn't work.

So it would seem the bigger problem isn't that the POH is off but that people don't read it...

[172driver]

POHs may be 40 years old, contain figures established by an ace-of-the-base test pilot in a brand new ship. Fair enough. They do, however establish something very important - a DATUM from which we can work.

Anything below POH figures and you are in test pilot territory

[Rod1]

“Anything below POH figures and you are in test pilot territory”

Yes I know, it is huge fun. My MCR has a POH, but it does not cover the CS prop I have, as well as the equipment fit. Establishing my SOP etc has been great fun and perfectly normal in the home built aircraft world, provided you have the experience to get clearance from the LAA (10 hours on a similar type and min 100 P1). My general aircraft performance is better than the std POH, which means either A) I am an ace test pilot and a superb aircraft builder, or B) my prop is better than the factory one. Unfortunately I think I know which is the most likely

Rod1

[moggiee]

Originally Posted by G-EMMA

moggiee If you can find me one published report that in any way points the finger I will change my view.

Try the Kegworth 737 for a start - everyone gets a share of blame there. Then there's Tim Lancaster's BAC1-11 spacewalk (window blew out because the engineer used the wrong bolts) and the Staines Trident where the crew retracted the leading edge flaps when they should have brought up the trailing edge devices.

In all three cases the causes were HUMAN ERROR and as such, human error is directly attributable to an individual or individuals. When an investigation says that a particular individual has made a mistake, that IS apportioning blame - it can be no other way. Those individuals may not be punished (that's a different issue) but if the report says that people X, Y and Z made mistakes then that is blame being apportioned.

There are plenty of others - but you will no doubt disagree on some tiny of semantics and nitpicking detail, rather than looking at the broader picture.

By the way, I have been one of those individuals who has been a factor in an incident (but not accident) and have no problem with taking a share of the blame. In my case I was a contributory factor in an incident on a long haul airliner on which I was FO, an error of omission in this case. I did not stop the Captain and Flt Eng breaking the rules (getting airborne with a tech fault and VERY nearly causing the aeroplane to crash) and I take my share of the blame and tell people about it in the hope that they may learn from my mistake. It is a failure to accept responsibility for your errors or even to accept that you could be wrong that is a problem. The Kegworth chaps don't accept that they made mistakes - so are unlikely to learn from them. I accept that I have made mistakes in an aeroplane and endeavour to learn from this.

Learning from mistakes is what the AAIB "mission statement" is about.

Mind you, I can't see you changing your mind as promised - that's not your style, is it? You prefer to nit pick a turn of phrase such as "dim view" when the intent in that phrase was perfectly clear.

The CAA on the other hand might, but I would like to see a report or prosecution relating to a light aircraft in the UK that cites the use of a non-approved check list as causal or contributing factor in either an accident or prosecution.

That wasn't/isn't the point at issue - you have combined 2 or 3 separate points to narrow a discussion down to such a level that you can use an exception to attempt to prove your rule! The CAA prosecute when they feel it's needed (although not as often as they should). Those prosecutions tackle human factors transgressions and as such are pointing the finger at people who have been found (by investigations) to have broken the rules.

With regard to the POH, as stated by others it may not be perfect but it is the best info that we have. It gives something to work with and, therefore, is ignored at the users peril. Safety factors built in should allow for age as long as maintenance is up to scratch - and whilst the odd genuine accident does occur (where a component failure was beyond anybody's control), the vast majority of accidents are human factor failings which could have been avoided by proper planning, decent decision making and adherence to rules and procedures.

[moggiee]

G-EMMA, I'm not going to waste any more time on you after this post.

I suppose you will say that I know I'm wrong, that I can't hold an argument etc. but the truth is that you are just a tiresome oxygen thief who can't see the bigger picture and trying to reason with you is a waste of effort! You may have noticed that you are in a minority of one - that means something!

If the facts determine the blame and the AAIB determine the facts - well, any half wit can put two and two together (so why can't you?). The AAIB say that part of their job is to determine the "causes of accidents" - if those causes are people then those people are responsible for the accidents, that is simple logic. If you are responsible for an accident, then that is another way of saying that you are to blame - it's not a difficult concept. They don't apportion blame or liability in a legal sense - that is for the CAA and the law courts - but they do apportion responsibility which, in a non-legal context, is the same thing.

Good night - try not to choke as you chew on your dictionary whilst attempting to elevate pointless pedantry to Olympic levels.

[411A]

When the FAA certified general aviation aircraft years ago under CAR3, single engine aircraft were, in my opinion, given rather short shrift.
Much of the information contained in the POH of these earlier aircraft was of a rather general nature, and as been pointed out by others, the performance data was obtained with a brand new aeroplane, with an experienced test pilot at the controls.
Most twin engine aircraft, however, had an Airplane Flight Manual, and with these aircraft, much more detailed performance testing was done, so that the performance information contained in their AFM's was of a better quality.

Newer aircraft, certified under 14CFR23, have a much better POH/AFM than the earlier types, and even with newer single engine aeroplanes, generally speaking, the performance data can be relied upon, while at the same time, using that one commodity that most general aviation pilots should have....a large dose of common sense.

And yet, as I watch some newer 172's taxi past my private aeroplane at the airport, there they go, with 4 good sized adults and much baggage stuffed inside, and no doubt with the fuel tanks full.

Clearly, with some pilots, common sense, never mind the actual performance data...is out to lunch.

[bjornhall]

When an investigation says that a particular individual has made a mistake, that IS apportioning blame - it can be no other way.

The concept you are loooking for is blameless error. See J. Reason et. al.

[A and C]

The lack of use of the POH starts from day one of a PPL's training, the problem lies with the fact that the document forms part of the C of A of the aircraft. As such most operators are very reluctent to let the aircraft POH out sight because students have a habit of taking them home by mistake.

The trouble that results from this can ground an aircraft at C of A renewal time.

Part of my PPL training course is an aircraft technical quiz that is usualy given on the first day that the student has a flight canx due weather, it involves finding a lot of technical detail using the POH thus introducing the PPL student to the book at an early stage.

[SNS3Guppy]

Why is it that, as far as I can see, every time someone asks a question or for advice, about the operation of an aircraft, most people simply jump in with their own favourite method, list, etc? Surely when a specific question is asked the correct thing to do is point the enquirer in the direction of the POH?

Perhaps because there's more be discussed than simple "read your manual." Perhaps because one might learn something by expanding on the topic, rather than simply "read the manual." Perhaps because there's more to the subject, than simply "read the manual." Perhaps becuase the manual isn't always comprehensive enough to address the topic, perhaps because occasionally the manual is wrong, perhaps because occasionally one may not encounter exactly what is spelled out in the manual. Perhaps because when one encounters the problem, there won't be time to consult the manual...but there's plenty of time to discuss the situation now.

I've had events occur in the airplane that weren't in the manual. I went to school for one type airplane after a year of flying it; in that recurrent class of eight, we were queried as to what emergencies and abnormal events we had experienced in the past year. Between the eight of us, we'd experienced everything in the manual, plus a number of events which weren't.

Several years ago while flying a foriegn airplane with a flight manual written in a foriegn language and poorly translated, and then only translated in part, I experienced an aerodynamic control lock, extreme buffet and vibration, and inability to control the airplane, within the published numbers that ought to have been considered "safe." This certainly wasn't in the book (which was prefaced by a sticker on the cover that said in essence, "nothing in this book should be relied upon or believed." I kid you not). Nor would there have been time to look it up, assuming it was readable or translated, when it occured. Three of that type have had inflight wing separations...nobody had any time to look it up then, either...and it's not in the book to look up even if there were time to do so.

A common discussion regarding light airplanes involves Cessna's recommendation against slipping with full flaps in the 100 and 200 series airplanes. All sorts of wild ideas abound, compounded by the fact that Cessna doesn't explain the reason in the flight manual. Most who expound on the subject don't have any idea why, but come up with some wild guesses. A discussion on the subject doesn't just address the subject itself, of course; because background and understanding of the aerodynamics involved are important...it benefits the listener beyond a simple "read your manual." And so it should.

Captain Al Haynes had never received training on, or read any papers discussing, nor found any referrences in his Aircraft Operations Manual regarding a complete control loss and full loss of hydraulics, when it happened aboard UAL 232. Never the less, on board was an individual who had developed his own methods for handling the airplane in the event just such an occurence ever happened; he came forward and volunteered what he'd learned in his studies, and the result when putting it into a crew coordination situation was that a lot of lives were saved. Again, not the manual, but fully deserving of much deeper consideration than just "read your manual."

Cessna has included the Fuel Flow Fluctuation procedure in their 200 series Cessna manuals for some time now, but the procedure is wrong, completely overlooks the chief cause of the problem, and using the procedure in the book can result in an unrecoverable engine stoppage, instead of a quick and painless power restoration.

I've flown several aircraft that were so heavily modified that reference to the aircraft flight manual was utterly worthless for any understanding of systems, performance, or procedure. In fact, one type differs enough that it's difficult finding two of the same type aircraft that are similiar enough to compare one to the other...from radial to turbine power to vastly different fuel, hydraulic, electrical and other systems on board...they don't even fly the same, perform the same, or handle the same, let alone work the same...discussions therefore should justifiably go beyond "read the manual."

It may save your life, or it may just help you come to understand your own airplane a little better. It's certainly worked for me.

[FREDAcheck]

...the document forms part of the C of A of the aircraft.

And as such, describes the certification, and doesn't necessarily describe "normal" flying.

For example, the Piper Cherokee 180 PoH chart for take-off distance specifies rotate at 80mph (70kts) with no flaps. Max all up weight, 20C, no wind, tarmac, requires 2250 feet including a factor 1.25 additional margin. A more normal departure with 25 degrees flap and rotate at 65mph (56kts) would probably do the same in under 1700 feet.

I would never suggest ignoring the PoH, but it may not be the only source of information.

[Redbird72]

Writing as a "once a week" ppl student, the reason I consult prune with questions best pointed at my FI/the POH is that they are both generally 20miles & 5 days away when some question or worry is eating at me.

The discussions on here give me enough food for thought and general guidance to stop me going insane before I can next get to the club and pounce on my FI with the self same question - and get it answered from the horses mouth.

I would never take anything I read on an internet forum as gospel and ignore my FI's instructions in favour of it although i may use it as a discussion point with my instructor.

[Final 3 Greens]

And yet, as I watch some newer 172's taxi past my private aeroplane at the airport, there they go, with 4 good sized adults and much baggage stuffed inside, and no doubt with the fuel tanks full.

411A, as usual, makes an incisive comment about the common sense of the above.

I believe that the marketing departments of the 60s and 70s promoted aircraft like the 172 and PA28 as 'flying cars' and the handling of these aircraft was engineered to be benign. The V tail Bonanza earned a reputation as the "forked tail doctor killer" and a hot ship, whereas in reality it is just a higher performance aeroplane that needs a defter touch than the 172/PA28.

As a result, if one learns on a 172 or PA28 (or even transfers across with low hours) there is a tendency to become a little complacent and forget the appropriate airmanship.

Unfortunately, the refresher experience can be brutal for the person who pushes the envelope too far, as even the most benign aeroplanes will eventually bite.

W&B takes only a couple of mins to calculate and is a potential life saver.