I found this at the IMDb site (regarding a scene in ‘Apocalypse Now’):
“Factual errors: The maximum gross weight of a Huey helicopter is 10,500 pounds. It would be impossible for such an aircraft to lift a Patrol Boat, Riverine (PBR) which weighs anywhere between 15,000 and 19,000 pounds.”
Does the actual weight of a flying machine limit it’s ability to generate lifting power"
If the above statement is true, how, then, did they do it?
Well, a Huey really can’t lift that much. This site gives max weight (craft, crew, load, everything) at 9,500 lb. A typically configured Huey would only be able to lift a couple of thousand pounds at the most.
I don’t know how they did it if that is what the movie really shows.
The easiest way to to this would be to have a plywood boat that only weighed a few hundred pounds. By the magic of movie making, cut to the next scene and you have the real boat + surfers and machine guns.
No, weight isn’t the limitation. Other things being equal, the less an aircraft weighs, the more it can lift.
The important other things are available power, wingspan and wingloading (in the case of a helicopter, disk loading), etc. Very few helicopters would be able to fly at twice their own minimum flying weight (i.e. their weight with pilot and minimum fuel).
You misunderstand the term “maximum gross weight” (max gross). Max gross is the SUM of aircraft, fuel, crew, arms, AND PAYLOAD.
Typically there will also be a several max payloads specified. This is related to the structure of the airframe between where the load is carried (floor, hoisting point, landing strut, etc) and where the lift is generated (main rotor) Very few aircraft can carry both max payload AND full fuel. Some aircraft can’t carry max payload even with NO fuel. This would most often be due to added equiptment that uses up some effective max gross rating.
This specification allows for some regulated level of performance, e.g. ability to climb at 200’/min, Ability to autorotate without damage beyond landing gear, or some such…so aircraft do not typically fail to fly at 1 or even 100# over max gross, but the crew is eroding the design safety factors…an insurance company could and probably would deny a claim if it could show the aircraft was operating beyond max gross.
These safety factors are in low tens of percent, not hundreds.
So what the statement means is even if the helicopter weighs ZERO, carries no fuel , and no crew, hanging that boat from it will still put it at about twice it’s max rated flying weight. It is inconcievable that any aircraft would have enough safety margion to be able to fly at all with such an overload.
That should read: “Gross weight is…etc”
“Max gross” is the number on the aircrafts specifications.