What determines the maximum airspeed of an aeroplane in straight and level flight?

Question

Ok, the answers i'm getting so far are not technical enough boys and girls. Many thanks though.

Is the volume and shape of the wing span, the density of the air at a given altitiude and the induced drag have anything to do with it?!?

Answer 1

Newtons second law - blance of momentum.

When the force acting on the mass to accelerate it is the maximum that the engine, atmosphere, and gravitational attraction to the earth can produce, and those forces are balanced by the the forces acting on the mass to slow it down, then the mass is at its "max speed".

Density of the air is affected by altitude, temperature, humidity, and weather. For horizontal, noncompressible flight, that density is a major component of the "dynamic pressure" and therefore the drag.

A very simple model of drag is D=0.5*rho*U^2 *Cd*A where rho is the density of the working fluid (atmosphere), U is the freestream speed of the air, Cd is the coefficient of drag of the airplane, and A is the frontal cross-sectional Area.

If you set max thrust equals this drag, then you can math out what U is, and call it the max speed of the plane. If the plane has a headwind or tailwind then its absolute speed will vary.

If the plane approaches mach then stranger and more energy-demanding phenomena kick in. If the plan is going beyond the speed of sound there is a third, also complex description for the drag.

If you are using a prop driven plane then you cant just assume that the thrust equals the planes horsepower, you have to consider the efficiency of the prop and there are equations for that.

Determining the Cd for a plane is complex because the wing, body, and tail all interact to change the overall Cd.

Answer 2

Firstly the engines as they are what provides the thrust. For jet engines performance will vary depending on air density and temperature. At low temperature more fuel can be pumped in without overheating the engine. At low air density the engine is less efficient (this is counterbalanced by lower air resistance on the craft). Jet engines need to be designed for an operating envelope with a range of conditions, they will operate best if the air flow gives the best angle of incidence on compressor and turbine blades hence air intake speed is another factor (as well of course as the speed of rotation).

The other factor in airspeed is the aerodynamics and structural strength of the craft (including vibration and for very high speeds temperature resistance). In general a good aerodynamic shape minimises the energy wasted in producing trailing turbulence and eddies.

Answer 3

it's mostly about the material that's used to make the plane... for high speeds, materials that can withstand heat and high stresses is used. for an example, in commercial planes Aluminum is commonly used to make the air frame of the plane, but if you search for information about the USAF SR-72 Blackbird, you'd find that its body was made of Titanium, which is known for holding its shape and properties under extreme heat and stresses as it has to fly at nearly 3.5 Mach, and a lot of heat is generated due to the friction with air at such speeds, I don't know if this is important or no, on Discovery channel there was a man who was working in the US intelligence in the former USSR saw some reports about planes that flew at 14 and 16 Mach, though it was unmanned, he said that it used some technology that ionizes air in front of the plane creating an almost friction free region in front of it allowing it to get to such high speed but like i said it requires some special material as well as the aerodynamic design and the propulsion system used which are also very important

Answer 4

the maximum speed is determined by the thrust produced by the propulsion system.. jet? propeller?... and the drag created by the aerodymic design.. when these figures are equal (but opposite direction) then you have reached your maximum speed... note that at higher altitudes where the air is thinner you get less drag but you also get less thrust unless you have a rocket.

Answer 5

The amount of energy spitting out the back of the engine

Answer 6

engine power to weight and aerodynamics plus physical properties of travelling through the atmosphere.

Answer 7

THE MAXIMUM SPEED OF AIRPLANE IN TODAY'S WORLD IS EQUAL TO SPEED OF SOUND IN AIR i.e. 332KM/S AND EVEN
WITH TECHNOLOGY MORE SPEED IS GOING TO BE ATTIANED AND A MATTER OF FACT THE SPEED OF ROCKET IS MORE THAN THIS VERY MUCH AND THIS WHOLE IS DEPENDENT ON NEW TECHNOLOGY AND MINDS SPEED AND HARDWORK OF MAN

Answer 8

Primal fear ?