Would you or do you takeoff above MTOM?

Peter,

If the insured and the pilot are the same in Switzerland they will come after you. I am not saying that a gear up landing will always be turned back in your face by the insurance company, all I am trying to say is that it won’t be as clear cut who is paying what until after the damage and if they can prove you have knowingly violated the POH’s limitations they will try to offload part or all of the damage to you.

Flyer59’s question of overloading the aircraft by 30lbs is similar to asking do you drive 10mph faster on the motorway than allowed. 90% do, whether it’s 30, 10, or 5lbs, doesn’t matter, it’s more than is allowed and until nothing happens and you will not be caught you won’t know the consequences.

Some aircraft have artificially reduced MTOW such as the Jetprop….many late 80s Mooney M20Js are eligible for a 160lb increase in MTOW simply by installing an ASI with slightly different speed markings….I would have no problem flying such a Mooney slightly above the old MTOW…..just sayin’

Whenever I take an adult passenger I fly overweight. As do 90% of 3-axis ultralights. If you see the typical Rotax-powered two-seater with two adults in it, you can bet it is overweight by at least 10%. This may aggravate other problems, but I have yet to see an accident report for this category of plane where overweight was cited as the prime cause. Afrter all, very often the same airframes are also certified as LSA’s, suddenly getting a 600 Kg MTOW (and yes, I remember from an earlier discusion that there is at least one manufacturer in CZ who does have separate designs for each category, but that is really the exception).

placido wrote:

whether it’s 30, 10, or 5lbs, doesn’t matter

In small GA aircraft where things are often approximated (especially fuel quantity as well as passenger weight which even in commercial operations you should “check by looking at the person”) can you be as exact as 5lbs? I can’t.

If the insured and the pilot are the same in Switzerland they will come after you

In that case what is the point of insurance?

For any particular aircraft, what limits MTOW may be different things, but I would guess it is strongly connected to stall speed

@Pilot_DAR is the expert on this stuff but AIUI MTOW is tightly related to Vs in that you need elevator authority at Vs (obviously, otherwise Vs is not Vs) so if you are loaded above MTOW, Vs has increased.

When the TBM700 went to the C2 variant Socata increased Vs from 60kt (the standard certification limit for SE aircraft) to 65kt (by convincing the FAA of improved crashworthiness – EASA took a few more years to accept this) and this gave them a massive increase in MTOW – because of the increased elevator authority, more wing lift, more aileron authority, etc.

I reckon a 1% increase in weight needs a 1% increase in Vr and needs a 2% increase in the takeoff roll.

In discussions with quite a few SR22 pilots, it is quite common for the SR22 to take off above MTOW especially for longer flights where the weight will “burn off” before landing.

Normally this is less than 100lbs(45 kilos).

The engine and airframe can certainly handle the extra weight with power to spare.

I believe that the MTOW in the G1 to G3 was based on the stresses on the parachute and not on the flying characteristics. The G5 has essentially the same engine and airframe and has 200lbs more MTOW.

I reckon a 1% increase in weight needs a 1% increase in Vr

That sounds reasonable: lift goes with the speed squared so a 1% weight increase requires a sqrt(1)% speed increase – with a bit of rounding here and there.
However a 4% weight increase would require a 2% speed increase, with the rounding errors a bit larger.
How that translates to take-off roll I have no idea, but can’t that (and several other factors discussed) be deducted or extrapolated from the performance graphs in the POH?

As a former load controller for airliners and having worked in that field for several years, my answer would be absolutely in the negative.

No, I would not take off in a known overload situation. The MTOW/M is the limit the airplane manufacturer has set. It may be regulated down by temperature, runway lenght, surface conditions or similar circumstances, but it can never be higher. If you knowingly take off in such a condition, you violate the law.

Yet, it is also perfectly clear that there will be take offs in such conditions. In GA planes as well as with airliners. The reasons are different however.

In airliners, passenger and hand luggage weight is calculated by average and in most cases below reality. I am not current on the figures IATA uses these days, when I worked in that field they were 83 kgs per adult, 38 per child and 12 per infant. That is with handluggage. Clearly, that is pushing the truth. The excess weight is however well distributed in the cabin and considered within tolerance.

In GA, we often enough get overweight conditions because either nobody does a proper wnb or they use “airline methods” to do it, that is they use always the same standard weights by passenger rather than asking the people to step on a scale, which some might refuse. Others, if asked, lie about their weight. So also there, the potential for overload is huge. Add to that, a lot of airplanes have such mediocre payload that they are overloaded even with “normal” people and any reasonable quantity of fuel on board.

As a former WnB instructor, I ask my pilots to complete a loadsheet (which is an excel sheet) before departure to be safe, legal and to make a point. As far as I know everyone does it, also because they know that it is in their own interest. Awareness helps.

The example with 30 lb fuel is of course provocative, as most people would say, ah, humbug, this won’t hurt us. And technically and physically that is probably right. But it’s an attitude problem. If we allow a bit of leeway there, a bit here, then situations can escalate. The question is why do we do that. Again, if you start taxi with 30 lb fuel too much, you still have the possibility to get rid of it by burning it before take off. If you do take off with it, not much will happen, that is obvious, as the fuel will probably be near the center of gravity and won’t even be noticable. And it will be gone fairly quick, 5 USG are burned within 20 minutes or so. But again, why push the limit if it’s not necessary.

Clearly, there are special flights such as ferries, atlantic crossings e.t.c. where overweight conditions are used regularly but are also approved by the competent authority. There is not much wrong with that, as long as the pilot in command knows what he is doing, possibly gets advice from people who have done that and so on. If such flights are planned, then the way to do it is to contact your responsible CAA, they will help you.

I would think, most overweight take offs happen due to negligence not intent. That is no excuse, but it is the reality. Questions like “how much is tolerable” are misleading because the answer has to be “Zero”. In the end, it is the pilot in command who has to figure out what to do, to go anyway, to burn the fuel off, to offload some baggage or even passengers. But whatever, it is always better to be safe and not fall for the “xx kg won’t matter” trap. Because even if you do reduce the “known” weight, chances are that you are heavier than planned anyway.

A special case are the “1999kg” STC’s, where the structural MTOM/W of a plane is regulated to 1999 kg in oder to save airway taxes. There, I’d have to say that going to the structural MTOM/W is something just about everyone does. Primarily because those planes become useless without it. In such a case, where you take off within structural MTOM but outside stc’d legal mass, it is purely an insurance problem. I’ve seen accident reports where it was mentioned but at the same time indicated that the exceedence of 1999 kg was not deemed a factor due to the higher structural weight limits which were observed.