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]

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):rolleyes:
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 :E

[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:suspect:

Rod1

[moggiee]

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 :eek: 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.

[BackPacker]

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.

That's the spirit!

I'd like to point out one other thing though. It's a good idea to keep copies of POH (either on paper or electronic) around but most of those I've seen (and have at home here) only contain the core POH, and not any supplements/updates because of various bits and pieces of equipment that have been added/removed over times, or changed insight from the manufacturer and so forth. So for performance-critical stuff (instead of just general interest stuff) always consult the POH of the aircraft involved, in full (including its supplements) instead of your own electronic or paper copy.

As an aside, the aircraft I flew in Florida when doing my PPL had their POHs attached to the seatback pocket with a thin steel wire. The only way to consult them was when seated on the back seat. AFAIK they never lost a POH but nobody read them either, relying instead on the paper copies they sold in the pilot shop (for a reasonable price I might add).

[Zulu Alpha]

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?

Often the information is not in the POH. eg many homebuilt/PFA/LAA aircraft do not have all the detail that is in a Cessna one for example. I asked about rpm/MP settings for 75% power for a Lycoming AEIO360. It isn't in my manual, but is in the Bulldog manual which uses the same emgine. I don't have a starting proceedure in the manual etc. etc.

Lots of prams without rattles over the AAIB. I think the reason they day they do not apportion blame is so they can't be sued. Personally I prefer their detailed reports as they are and find them useful.

ZA

[172driver]

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.

I find this quite shocking. The very first thing my instructor (in the US) did, after we had decided which type of a/c I was going to learn on, was to make me buy a copy of the POH. IIRC it cost about USD 10.- and I still have it.

Are FTOs in the UK not able to use a photo copier :ugh::ugh: ?

[A and C]

I whole hartedly agree but I am just telling it like it is.

[Redbird72]

Lots of prams without rattles over the AAIB. I think the reason they say they do not apportion blame is so they can't be sued

I was fortunate to attend a presentation by the AAIB the other week, and the reason they gave, was to ensure people give them full and complete information after an incident or accident.

The speaker felt quite strongly that if they explicitly apportioned blame or routinely allowed themselves to be involved in legal cases then future investigations could suffer as a result.

[gasax]

I have to say that the first tme I read the POH was when I had about 35 hours - ppl in the mid forties (when the 'approved course was 38 - of I remember correctly).

But they can be very over rated. My last certified aircraft had a variety of detailed charts for ground roll and en route climb at any number of density altitudes. And a whole bunch of other really really important stuff - including parachuting (including warnings that if the parachutist opened their chute prematurely then it may foul the tail!!!!!

But it had no, I repeat NO fuel consumption figures. And as it had an engine reknowed for oil consumtion nothing about that either.

So the first 20 odd hours were about establishing a baseline - much as I have done with my current permit aircraft. And any PPL can do it. We fly simple aircraft that have simple characteristics - it is not rocket science!!!

If you have an aircraft with odd techincal features the POH may be very useful. If you think you can match the figures then reading thr POH is pointless - if you want to use to to add some fat and happy factor then they are pretty useful.

[IO540]

The original Q is a correct Q to ask in a rhetorical manner but the words 'pot' and 'kettle' come to mind in this case, as indeed in so many scenarios in GA....

Today's Cessna/Piper spamcans were designed in the post-WW2 years when people were thin and hungry. Yet people see the 4 seats and think they can fill them, but they can't with today's obese Americans or Brits. You could actually fill them - with size-8 females but there aren't many of those around 50 years later...

The training business routinely overloads planes and this teaches students that it is OK.

In reality it is OK to go a little over (so long as one doesn't load forward or behind the envelope) but one needs more runway and one needs to know how to work this out, but this isn't taught.

The AAIB might like to preach that people should not overload and they are absolutely right but if they want to tackle the real cause of the problem they need to start at the beginning (PPL training, and eating habits).

[SNS3Guppy]

And a whole bunch of other really really important stuff - including parachuting (including warnings that if the parachutist opened their chute prematurely then it may foul the tail!!!!!



While you may not find that important, I've seen the results of failure to heed that very warning...personally. I saw a jumper on a load I was on, several years ago, nearly sever the horizontal stab on a Caravan when he didn't dive clear.

Not everything in the manual will apply to every flight, but you should always be thoroughly familiar with the manual and the procedures it contains. There is absolutely NO excuse for failure to digest the aircraft flight manual, and to use it.

[betterfromabove]

I'm so glad someone has brought this topic up, because I know it's a question most PPL students pose during their training.

We are taught to add in a "safety factor" & yet the ideal conditions in which the performance data are often obtained are quite the opposite!

Always puzzled me why the manufacturers are not forced to do more realistic tests to give "real-life" figures. Is it to do with cost & the already lengthy certification process?

But, what is that process for unless we certify aircraft that are "safe" (whatever definition you choose for that...) for the average pilot to go use...?!?!

I've flown at a good dozen schools/FTO's & only a minority point you in the direction of the POH without you having to go look for it, either in the building, the aircraft...or the internet. Not once has the checklist been usable straight off the bat, even for a spanking-new DA40.

What do people think about posting POH's online? Not decided myself, as it seems to circumvent all the checks & measures put in place to avoid misrepresentation. Yet, providing we use the sensible provisos & see the POH as the guide only that it is, should we not take the information from wherever we can.

That's the trouble with aviation, there's rarely a "one-stop" answer to a question.... things change, rules don't agree between countries, the lawyers get in & fiddle with common sense, the high cost of testing thing to the n'th degree sometimes comes into play...

Only way forward I can think of is to read everything you can, as regularly as you can, ....then go reread it when you think you might be forgetting it, ...take copious notes, read some stuff just for the hell of it (like PPRUNE...I learn something every logon), speak to everyone you can find who knows more than you do, read St Exupery, read Gann, all the pros, then go fly...

The most important information when all goes wrong is that you have in your head...

Fly safe
BFA

[SNS3Guppy]

We are taught to add in a "safety factor" & yet the ideal conditions in which the performance data are often obtained are quite the opposite!

Always puzzled me why the manufacturers are not forced to do more realistic tests to give "real-life" figures. Is it to do with cost & the already lengthy certification process?

But, what is that process for unless we certify aircraft that are "safe" (whatever definition you choose for that...) for the average pilot to go use...?!?!



Hold the phone for a moment there. Perhaps there exists a great deal of misunderstanding regarding certification and the data derived there from...but let's not carry that to the conclusion that the airplane you're flying is unsafe.

Certification means that your aircraft design must meet certain well established standards of performance, construction, etc...and your airplane meets that. Different standards exist for some aircraft, than others. The performance standards for a light twin such as a Cessna 310 differ substantially from a transport category airplane such as a Learjet, for example. This doesn't mean either one is unsafe, but it does change what you can expect from the data given you.

Adding a "safety margin" is always a wise idea. I can gaurantee you that I always do in terms of performance, fuel reserves, etc.

Some talk has been had regarding heavy performance of a light single; load it up with four adults, what do you get? You'll get essentially what the book says you'll get...but it's not gauranteed. The book performance numbers are demonstrated numbers, many of which have been interpolated or averaged when the aircraft was demonstrated during certification. A good example is your maximum demonstrated crosswind component. Can the airplane handle more than that? Almost certainly. However, what you're told with this figure in your aircraft flight manual (or pilot operating handbook, as you will) is that this is the highest number demonstrated during certification. Perhaps that's all the crosswind component available that day; perhaps there just wasn't a bigger angle with the runway at the test and demonstration facility. Perhaps the manufacturer doesn't want the liability of publishing higher numbers...but that's all it is...a demonstrated number.

In the United States, light airplanes have long been manufactured and certificated under the code of federal regulations, title 14, Part 23...often just called "Part 23 airplanes." Under Part 23, the performance standards aren't nearly as stringent as transport category airplanes, nor is the expense as high in getting Part 23 certification. A part 23 multi engine airplane, for example, doesn't need to be able to execute a balked landing or go-around on one engine...whereas a transport category airplane (such as the learjet mentioned before) must be able to do so. A light twin doesn't even need to be able to hold altitude after losing an engine...and many can't. Not the case with transport category.

In a light single, that's really quite irrelevant. You're going down either way. You're presented with other meaningful data, however. Takeoff distances and climb rates, for example. These are what were demonstrated using new demonstrator airplane, with a test pilot on board, and may well represent the best that can be expected. The performance is dependent on having the same thrust available, the same technique available, the same tire pressure available, etc. If you're slow to act, if the engine on your rental isn't quite as strong, if the tires are a little low on nitrogen, etc...you may take longer to get off the ground, climb slower, and burn more fuel.

The AFM/POH isn't there to prevent foolishness, but only to give you the performance and procedures that were demonstrated to work at a point in time, long ago. They are provided by the one entity most uniquely qualified to give you that information; the manufacturer. In many cases, you are legally obligated to operate within the confines of the data you are given.

If an instructor fails to thoroughly explain the aircraft flight manual and insist on it's use by a student, the instructor has failed legally, and most certainly morally. One cannot, and should not ignore the POH. The old saying "if all else fails, read the directions," does NOT apply in an aircraft. One should be intimately familiar with the aircraft flight manual.

Every aircraft I've flown, from big to small, has always been learned by learning the aircraft manuals, making flash cards, digesting what's offered, and then going beyond to learn everything I can about the airplane from the maintenance manual, training guides, industry publications, etc. People sometimes are a little too quick to dismiss light aircraft because after all, "it's just a little airplane." The thing is...which one will make you more dead...the F-18, or the J-3? The J-3 just kills you a little slower, that's all. But not by much.

Every aircraft should be taken seriously. When I was a civil air patrol cadet, I participated in a search for two fighter pilots who had rented a light airplane for the weekend. They ended up in a place called Snow Canyon, and were found buried under snow. In their fighter, they could have powered out of that canyon and climbed to safety when they got themselves into a bad spot. The light airplane didn't do that for them, though. They couldn't outclimb the terrain, and instead impacted into a canyon wall. Two well qualified individuals who failed to respect the airplane. It killed them just as dead as their fighter jet.

The AFM/POH/AOM is there to give you valueable information. That information ranges form how to manage fuel to how to store the aircraft and engine for extended periods. It explains aircraft systems...something vital to know regardless of what you fly. It provides limitations, performance charts, etc. There is no excuse for failing to consider this information and use it as far as you are able.

The numbers that are calculated from the book may not match the real world performance of your airplane. You should NEVER plan on a marginal takeoff, for example, when the book says you'll use all the runway and just make it over obstacles at the end. You might not make it. You should add in your own safety margins. Performance in the book doesn't use "built in safety margins," it's just what the airplane was once shown to do. Use it as your guide. If the available runway is going to be shaving it close, then back off, get rid of some weight, choose a cooler morning, get a longer runway, find one with less obstacles, etc. If your calculations show that you have a generous margin...you're only going to use half the runway and you've got ample climb...then you needn't be too worried about a slight difference between your actual performance and the book numbers.

I've seen fuel consumption in an engine double when a pressure carburetor failed. The amount of available fuel was cut in half because it went twice as fast. It can happen. Likewise a fuel leak out of sight...can reduce the "time in the tanks." Accordingly, I have a personal light airplane policy of never "burning off the bottom half." It's an old saying, that it's hard (but not impossible) to run out of fuel if you don't burn off the bottom half of the tank; if you always land with half a tank of fuel, you've always got at least that much fuel that's available. Now, I don't specifically use the half-tank rule, but I do allow very generous margins that I'm not willing to compromise.

Use your flight manual. But fly by PFR, or personal flight rules. You should never push the guidlines or limits of the flight manual. However, there is nothing that says you can't be more conservative. If the regulation requires 45 minutes of reserve fuel and the book says 6 gallons of fuel will give that to you, there's no reason you can't land with 12 gallons, instead.

I checked two individuals out in a Cessna 210 years ago. It had long range tanks. In the normal tanks, you fill to the bottom of the filler neck. In the long range tanks, when the fuel reaches the bottom of the filler neck, you still have another 16 gallons of fuel to put in...another hour in each tank. Fill the tank visually just to the bottom of the filler neck, and you've shorted yourself two hours of fuel. The fuel gauges may not tell you this. Both those individuals didn't feel like listening, didn't bother to read the flight manual on a regular basis to refresh their understanding of the airplane, and both of them made off-field forced landings when they ran short of fuel before reaching their destination. This is one good example of many where using the manual would have made a difference, as would a thorough discussion (which involves listening and remembering, on the part of the student) would have made the difference for the student.

Reading the manual isn't enough. Listening to others isn't enough. Take all the information you can get in order to obtain as thorough an understanding of your aircraft as possible. The life you save may certainly include your own. Don't just understand a part of the picture; take time to get to know the whole ball of wax.

Just think where Icarus and Daedalus would have been if they'd bothered to read the flight manual...;)

[englishal]

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.
Right :ok:

Most of the time the POH is either not around, or you are not allowed to take it away (in the case of a rented aeroplane).

Often flight planing is done at home, so if I'm planning to take a PA28-141 into a short field, and I usually fly a PA28-181, it is nice to know roughly what SF technique is and how many stages of flap I can expect. Then I know if I even have a cat in hells chance of getting out again and whether to bother any further with plan A.

[SNS3Guppy]

Englishal,

I certainly wouldn't bother asking others over the internet if they think you can make it.

I certainly would bother making a copy of the flight manual to bring home, to crunch the numbers. Know BEFORE you go.

I have the luxury of working somewhere that the numbers get crunched for me; I actually get a printout of what to expect, how much I can carry, even what fuel I can take. However, I do my own calculations anyway, not relying upon anyone else's opinion. I make a little crib sheet that includes the numbers that are given me, and compare them to my own calculations. If there's any significant discrepancy, then everything stops until it's sorted out.

We had a crew recently that departed some sixty thousand pounds overweight. Disregarding issues of actual takeoff performance, that makes a big difference in the fuel burn on a long flight...very possible to suddenly find that there's not enough fuel. They relied on the numbers that were given them and called it good. Very bad idea.

If you intend to go take a flight, show up to fly the airplane with the numbers already done, your flight plan already made, your charts marked, your notes made, your NOTAMs in hand, your weather prepared and reviewed, and your decisions formed in advance. Don't guess as to whether you can go. Know.

Use the manual in order to know.

[bjornhall]

Always puzzled me why the manufacturers are not forced to do more realistic tests to give "real-life" figures.

I can think of a couple reasons...

Obvious: Performance is a huge selling point, so you want the best figures possible.

Safety: If the figures are not optimum, using the best reasonable technique, people will start thinking "well, you could get better figures by using a better technique!". Then you get people expecting better performance figures than the POH says, and bending stuff/people when they don't. There is no such risk now, when everyone knows the POH performance is the best you can reasonably expect.

Problematic: What is "realistic real-life figures"? How much are you expected to screw up the procedures? Do you add 3 kts, 5 kts or 10 kts to the optimum speeds? Do you factor in a 1 second or a 4 second float? How much too late do you take the power off during landing? Just how far above the 50 ft mark are you when you pass it? The book figures used now are at least well defined.

[bjornhall]

As for the unavailability of the POH...

Just buy one! They are easily available and not expensive.

Yes, I know; it's obviously not the official POH, and there are some aircraft that are so rare/heavily modded/special that you can't find an applicable 'generic' POH/PIM/AFM. However, for what most of us fly, that is not a problem; a 1989 Piper Cadet will have the same performance as any other 1989 Piper Cadet, so a PIM for the right type, model, year and serial number range will work. Obviously, W&B stuff will need to be copied from the actual POH of the individual aircraft.

[Redbird72]

On Saturday (quite a warm day),I used a 152 that had just flown and had stood for about 25 mins.I didn't prime,and the engine spun for what seemed ages (prob only about 10-15 sec) and staggered into life.Difficult to judge whether it was starved or richShould I have primed or not?

Being a student, I can only comment on the 152 I'm learning on, but that one only needs a prime if I'm the first lesson of the day. 25mins after last use it starts on the button, regardless of the weather.

[betterfromabove]

SNS – Clearly you’ve a few more landings under your belt than me, so I don’t think there’s anything I can possibly add to your mini-treatise(!?), except perhaps to clarify my comment regarding what makes an aircraft “safe” in the hands of an average PPL, which perhaps got a little lost in translation…

Wasn't the safety or integrity of the plane I was discussing, it was the limits in which the aircraft should be used operationally, which are not always spelt out as clearly as they should be to students.

As we all seem to agree, the POH, while being the legally binding document, of course only tells part of the story. In the case of some of the more exotic or vintage types, it may give very little of the plot at all!?! And this is where we go chat to someone of experience, hopefully our instructor, if not, one of the type grandees.

To respond to one of the other posters, who suggested POH’s are easy to get hold of….I return to my point about whether using generic docs downloaded off the internet is such a good idea. My instinct is to say yes, it’s better than nothing, but on every occasion there will be further information to gather…sometimes the most crucial. I myself got caught out doing this when flying the DR400 for the first time….thought I was clever checking out exactly which model spec the club was using, downloaded a POH only to find they were using some exotic type of prop that demanded some very particular RPM management. Only found out when airborne. Instructor mentioned nothing in the brief. A classic demonstration of where we need the POH+instructor information combination.

As regards the point about what constitutes “normal” conditions, I agree it’s not an easy question to answer. There is a certain logic for the manufacturers in using a base-case scenario & leaving it up to the judgment of pilots to adding their own safety factors. Those of us who do so routinely keep ourselves alive with that simple act.

The issue is with the 4-up-&max-fuel-C172-brigade. Coming at this with my non-pilot, scientific, hat on, I maintain it’s strange that there is not a “calibration factor" applied.

Personally, I would prefer to know what a non-professional, moderate hour VFR-only PPL can achieve in a series of scenarios with a particular machine, rather than a hot-dog test pilot with a brand new airframe in ideal conditions. Call it the in-built safety factor if you like…