I wonder if I could take off with weight more than the gross weight stated in the POH of my aircraft as long as I take off with a higher speed?
I think I have done it once by mistake.
$\begingroup$
$\endgroup$
6
6 Answers
$\begingroup$
$\endgroup$
4
Can you take off over gross weight? Yes, it's possible on any airplane, dependent on how far over the weight limit you are, the density altitude, how much runway you have, what obstacles are in the area and other factors. It's very easy to go above gross in a Cessna 152 with full fuel and 2 passengers, and probably happens more often than people realize or own up to. That doesn't make it a good idea, which is why pilots are trained to do weight and balance plus performance calculations before every flight.
Besides the safety angle, taking off over gross weight could land you in trouble with the FAA even if nothing goes wrong, you can lose your ticket for that. If there was an incident your insurance may not cover damage or litigation costs.
-
1$\begingroup$ This pretty much boils down to, Can you? Yes. Should you? No. $\endgroup$– FreeManSep 20, 2018 at 12:00
-
23$\begingroup$ Close @FreeMan, more Can you? Maybe. Should you? No. $\endgroup$– GdDSep 20, 2018 at 12:43
-
$\begingroup$ What is the meaning of "how far over you are" - does it mean "by how much your weight is above the maximum limit"? $\endgroup$ Sep 21, 2018 at 7:52
-
1
$\begingroup$
$\endgroup$
3
Are you a qualified Test Pilot with insurance covering you for crashing this aircraft? The Max Gross Weight quoted in the POH tells you how far the factory Test Pilots have taken the airplane - any further and you are doing the experimenting. (An obvious concern is that with too much weight, the wings will fold in flight. But there are other concerns.)
There are margins, but you don't know what they are. So you might already have been flying within those margins, and thus got away with it. But if you don't know what the margins are then you can't guarantee to stay within them.
-
17$\begingroup$ This is generally incorrect. The POH is much more conservative than anything test pilots would have pushed the aircraft to and would incorporate engineering data, test flight data, and appropriate safety factors to come up with those numbers. The POH guidance is definitely not the maximum limit a plane has ever been flown to. $\endgroup$– J...Sep 20, 2018 at 14:01
-
1$\begingroup$ Probably more accurate to say that the limit stated in the POH is the maximum that the manufacturer is willing to guarantee it'll handle... $\endgroup$ Sep 21, 2018 at 8:25
-
$\begingroup$ Downvoting because of the incorrect assertion that the test pilots never took the plane beyond the POH. @anaximander suggests a very good modification to the original answer. Happy to upvote this answer instead, as it's a good one in spirit and tone, but it also has to be factually correct! $\endgroup$ Jun 27 at 13:47
$\begingroup$
$\endgroup$
3
One thing that hasn't been mentioned yet is CG. Often CG is what will get you. On many aircraft the places that you are putting the weight has considerable arm from CG. This means that you are also shifting the CG. I have seen for instance Cessna 402 loaded amazingly over gross with the load as far to the front as possible. However Google Aaliya death and you will see what happens when the CG is too far aft. All in all it's a bad idea to fly over gross, and it is death to fly out of CG especially aft.
-
$\begingroup$ This was my thought. I would say that going out of CG is much worse than going over weight. And when you're over weight, you're more likely to significantly affect the CG. $\endgroup$– ShawnSep 20, 2018 at 19:44
-
2$\begingroup$ The first sentence could just say Center of Gravity. Perhaps this is a recognized acronym, but I didn't recognize it immediately. $\endgroup$ Sep 20, 2018 at 22:42
-
$\begingroup$ @FaheemMitha I think in the context of aviation everyone should probably know what CG means. $\endgroup$– J...Sep 21, 2018 at 11:11
$\begingroup$
$\endgroup$
Physically, yes the aircraft can take off at or above MTOW - and depending on the aircraft and ambient atmospheric conditions, can takeoff and fly at a considerably greater weight than MTOW. The problem becomes that the values for MTOW were decided upon during design and flight test, taking into consideration a wide range of operating conditions plus design structural static and maneuvering loads on the airframe and landing gear. Unless you are very familiar with these numbers, you can risk structural damage to the aircraft during ground roll, stability during ground movement operations, maneuvering and landing the airplane. In addition, you have no known values for performance data on the airplane in terms of length of ground roll, takeoff distance to clear obstacles, maneuvering load limits, rates of climb and and climbing distances, stall recovery characteristics, etc.
Therefore, in loading an airplane beyond what the manufacturer states for an acceptable weight and balance envelope, you are now swimming in unknown and potentially very dangerous, waters. Otherwise smart and rational people die all the time doing stupid things like this in airplanes.
Additionally, intentionally operating an airplane outside of its weight and balance envelope is illegal, as it violates §§91.9(a),
No person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft flight manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.
Overloading also could easily be cited as a violation of §§91.13 Careless and Reckless Operation and §§91.7 Civil Aircraft Airworthiness.
The bottom line: Don't try it. You don't want to break the law or worse, find out the hard way that your guestimates on the plane's performance were incorrect.
answered Sep 20, 2018 at 20:25
$\begingroup$
$\endgroup$
5
This is a bad idea for a host of reasons, but structural failure is one of the worst. Sensitivity to gust load is increased when overweight, reducing the designers G load margin.
from Mountain Flying
Consider an airplane that has a maximum allowable gross weight of 3,000 pounds. If it encounters a +30 fps gust that results in an additional 2-g load factor, the airplane experiences a total of 3 Gs load factor. Multiply the 3-g load factor by 3,000 pounds and the wings are supporting 9,000 pounds.
Assume the airplane is loaded to 1,500 pounds and that it is subjected to the same gust. With half the inertia, the gust acceleration is doubled, causing the airplane to experience a 5-g load factor (4-g force plus 1-g level flight). Multiply 1,500 pounds by 5 gs and the wings are supporting 7,500 pounds.
The lightly loaded airplane is subjected to 1,500 pounds less load when encountering the same gust. Even though the heavy airplane realizes less load factor, it incurs more strain. The pilot recognizes load factor; the airplane recognizes load.
-
1$\begingroup$ This is mostly incorrect. Sensitivity to gusts is generally reduced with weight: a given gust will produce a certain additional force, which will translate to lesser acceleration on a heavier aircraft, while stressing the airframe just the same. However, this somewhat depends on whether you choose to fly at a higher AoA or higher speed. Then, maneuvering speed is determined by control factors and is increased with weight; basically, heavier aircraft will sooner stall than break when pulled hard. Overall, given enough runway, performance/stall will usually be your main problem. $\endgroup$– ZeusSep 21, 2018 at 1:40
-
$\begingroup$ @zeus I did not say sensitivity to gusts. I said sensitivity to gust load, the additional load you describe. A heavy aircraft flies faster and/or at a higher AoA, and will experience a higher gust load than one that is lighter. The heavy is also closer to its structural limit, so the additional load from a gust that a properly loaded aircraft could stand might break an overloaded aircraft. You can read this directly off the chart. Read the reference on AA587, which broke apart below maneuvering speed because the pilot over controlled in wake turbulence. That aircraft wasn't even overloaded. $\endgroup$ Sep 21, 2018 at 3:53
-
$\begingroup$ How do you produce a certain fixed 'gust load' to compare? It only makes sense to compare the same condition, i.e. the same gust. If you fly at a higher AoA (e.g. in cruise), but still far enough from stall, the effect of the gust will be practically the same (ignoring second-order effects). Only if you decide to fly faster will the 'gust load' from the same gust increase (but the feel/acceleration will still reduce). Yet this is hardly the most significant factor: you need a super-strong gust to exceed the design load in level flight. $\endgroup$– ZeusSep 21, 2018 at 7:38
-
1$\begingroup$ ...Maneuvering speed is by definition the one below which you can't cause structural failure by overcontrol, so AA587 was certainly above it. That said, it is usually specified for pitch control only, whereas technically it should be defined separately for each axis (or the slowest of them explicitly defined). Twins necessarily have a lot of rudder control, so in practice they may always be at risk. Either way, this is irrelevant; the fact is, pitch maneuvering speed increases with weight (as you can find in any POH): at a given speed, a heavier aircraft is closer to stall in level flight. $\endgroup$– ZeusSep 21, 2018 at 7:48
-
$\begingroup$ @Zeus The interesting point of the article was that training on maneuvering speed is misleading, and that you can cause structural failure below this speed. Your definition, and the one from the flight training handbook, is simplified to the point where is isn't really true. "Surprisingly, to nearly every pilot, Va is not a speed which at or below the pilot is allowed full unrestricted control surface movement without the danger of structural damage or failure." AA587 was at 2000ft and climbing when it came apart, way below Va. $\endgroup$ Sep 21, 2018 at 13:58
$\begingroup$
$\endgroup$
2
You should not do that; see the example of the Colt Richter who crashed his plane after overloading it.
http://www.ktva.com/story/38687378/witnesses-describe-pilots-takeoff-struggle-before-fatal-crash
-
$\begingroup$ From the linked article,
Price said Tuesday that, right now and at this point in the investigation, "I have no evidence to suggest that the plane was overloaded."$\endgroup$– egidSep 21, 2018 at 3:51 -
$\begingroup$ Yes, which is why I linked the other article stating the witnesses' testimony. $\endgroup$ Jun 27, 2019 at 21:18
...and your rate of climb will be much lowerIt won't necessarily be much lower, but it will be proportionally lower. Taking off at max gross plus one kilo won't be materially different from taking off at max gross, for example. $\endgroup$