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Would you or do you takeoff above MTOM?

I have that:

balancing lift with weight

const*v2 / 2 = mg

(const is aerodinamic coefs)

so v = sqrt ( 2mg/const)

time to takeoff = v / a
(where a = acceleration)
= v / (F/m)
= sqrt(2mg/const) / (F/m)

(F = force, m is mass)

d=1/2 a * t^2 = 1/2 a * v^2/a^2 (since a t = v / a) = 1/2 v^2/a = 1/2 v^2/ (F/m) = m^2 * g / (F * const)
(d = distance)

so increase in take off dfistance would increase with square of mass (in the limits of aerodynamics, as at some point the plane just can’t take off). accelerate -stop should then increase by double of square of mass.

Flyer59 wrote:


What i do not know: Can a scale where you put all three wheels on a pad, measure the CG? It would be great to have one of these for some tests …

You would need a separate scale for the nose wheel to calculate longitudinal CG

Last Edited by AnthonyQ at 04 Jan 17:30
YPJT, United Arab Emirates

Interesting question…

When I was first looking at Saratogas I asked for a copy of the W&B schedule, the Brooker (who I didn’t end up buying through) told me not to worry as long as you can shut the doors it will get off the ground!!!

He obviously hadn’t read the accident reports and had very little appreciation for physics, sanctity of life…or for that matter anything that didn’t concern his commission check!

I personally like to keep within limits and have come to accept my plane may have 6 seats but 5 is realistically the limit with any quantity of fuel.

The point raised earlier about ‘creeping’ up the mtow after each successive sucessfull overweight takeoffs is very valid. You probably won’t always be flying on a cold day with a Tarmac runway at sea level !

Alex
Shoreham (EGKA) White Waltham (EGLM), United Kingdom

Peter wrote:

It won’t if it is heavier…

Come on, I meant the Vr appropriate to the mass, of course.

ESKC (Uppsala/Sundbro), Sweden

I do fly overweight sometimes such as on the trip I did through Africa. Flying through Africa with a ferry tank we flew overweight all the time and not just by 30 pounds. We did have it all arranged ahead of time with the insurance company on paper, but it still was not 100% legal. If I were to fly only legal I could not have done the trip and there I decided to take that risk. We were loaded with fuel and flying through the desert in hot conditions with outside air temperatures reaching sometimes 50 degrees Celsius. I remember a few instances where we would hardly get off the ground. But we made it, had lots of fun, would not have missed it but were not 100% legal I think. :-)

Now, just recently I had a request from some people that wanted to fly with me to Courchevel in the Seneca 2. It would be me as pilots and 4 adult friends in the Seneca 2. No ski equipment as we would rent. I refused the proposal as I simply could not find a way to get the W&B working with the Seneca 2 with more than 4 people (it seats 6), full fuel and still be within the W&B limitations.

I think it is not a good idea in general to fly overweight. However, take the earlier mentioned Piper Jetprop DLX. Most pilots flying these great machines fly overweight and take that fact and risk for granted. So, it is not good, but it is still being done and if you do it or not is a personal call.

EDLE, Netherlands

All through my PPL training we flew overweight in a C150, I’d guess the instructor was 210lbs and I would be around 185lbs. We always flew full to the brim. It was winter, but Florida nevertheless. As a student I never gave it a second thought until it came to the skills test W&B calc. I asked the examiner his weight, his reply was under his actual by some way and still proved overweight in the C152. I pointed it out and he was fine with it.

How often do most do a W&B calc? Surely you know your own aircraft and only do it if you feel it is likely to be close? Insurance aside slightly overweight is not the concern out of CoG is. That said I wouldn’t fly our current little aeroplane overweight due lack of performance.

Why just pick MTOW to violate? Why not also exceed Vne or spin the plane despite placards prohibiting it? These limits are there for a reason. Violating them is both irresponsible and dangerous. When I see a pilot openly discuss consciously violating placard and POH limits I cringe. What else will this guy try?

In my mind this comes down to the question – how much is too much?

30lbs over MTOW will obviously not hurt you, but once that has worked well, how about 50lbs next time, then 70 and so on – you see where this is leading. Where do you finally draw the line? Human nature being what it is will always try to push the envelope, but there will invariably be the straw that breaks the camel’s back.

Personally I consider the POH MTOW the line. If I really have to ‘fill ’er up’ as I had to on a recent flight then I weigh every item and make a load sheet. And yes, the pax get weighed too in a case like this, if they don’t like it, they stay on the ground.

All that said, would I do a flight as referenced above by AeroPlus? Of course! But I would consider the implications, seek guidance from ferry pilots, etc.

The danger does not lie in a well-considered one-off, but in the ‘creep’ factor of pushing the envelope on a regular basis.

Mooney_Driver wrote:

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.

I think these figures are still valid and they obviously are pure fantasy.

Why just pick MTOW to violate? Why not also exceed Vne or spin the plane despite placards prohibiting it? These limits are there for a reason. Violating them is both irresponsible and dangerous. When I see a pilot openly discuss consciously violating placard and POH limits I cringe. What else will this guy try?

The above post illustrates why technical knowledge (aircraft performance, etc) is useful.

I think these figures are still valid and they obviously are pure fantasy.

I periodically have a lunch with some current Boeing/Airbus pilots and when I put this Q to them, they give the obvious answer: the runways they depart from are all plenty long enough… But maybe they are pulling my leg… can an AOC jet really go 1kg over MTOW? Or, if it does, the real figures presumably won’t be actually written on the load sheet. When I was PPL training, the tech log would be “creatively written”.

I have seen a presumably unloaded cargo 747 get airborne in about 500m… so if you know your 777 is say 2% over MTOW, and the runway is 2500m, you know you will be fine and with a big margin. But I wonder what the % of “human related load” is like in CAT compared to GA?

All through my PPL training we flew overweight in a C150

Of course; this is standard. Same in PA28s; with 3 modern size adults they are over max.

It has been claimed that this is the real reason why Cessna refused to restart the C150/152 (it could not be flown legally, except by a UK Size 8 female instructor and a similar size passenger) but was the 162 any better?

Administrator
Shoreham EGKA, United Kingdom

Thanks all :-)

@USFlyer
Sorry, but i think i made it clear that i’m not the type to violate the POH, but the way you reacted is a bit over the top

@Mooney_Flyer
I don’t buy the “attitude” argument, and i prefer to make my own decisions. It is more important to understand the POH than to follow it like bible down to 1 percent.

Every POH i know contains mistakes too and is never the “whole truth”. For example the SR22 POH says 77 knots for short field landings, but every specialist will use 77-1 knot per 100 lb below MTOM. I think that the right procedure is more important.

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