It is possible the reason ultralights slow rapidly and also accelerate rapidly, is because of low momentum. Low mass leads to low momentum, and drag has to basically overcome the momentum to slow a plane. So the same amount of drag can decelerate a MiniMax much faster than it can a Cessna 150 which has a gross weight 3 times that of a Max. The Cessna obviously has 3 times more momentum.
Inertia and momentum are terms used inter-changeably; on take-off since the Max has low inertia, it accelerates very quickly and gets airborne in no time. The common thread running in both scenarios is probably low mass of ultra-lights, though I guess it is mistaken generally to mean high drag. ( If the culprit was high drag, then a Max should take very long to get airborne. )
Sounds good to me, physics wise. Momentum is the resistance to change in velocity, something that weighs 3 times more with not that much more drag will take much longer to slow down. Ultralights have (i could be wrong) a lot of lift/drag because they have to operate at such low speeds, compared to larger aircraft, which weigh much more but more importantly have a lesser drag/weight ratio. RC planes can feel very heavy and sleek and take forever to slow down if designed to be like that, or they can be like ultralights and act almost like parachutes the moment you get off the throttle. I own both =)
So the key, as you are saying, is a drag/weight ratio that judges how they react in terms of acceleration.
I Absolutely agree it's the low inertia, perhaps with induced drag being a factor of weight and at these low speeds induced drag being a large component of total, they are potentially less draggy than standard ga's.. but as noted the drag to mass ratio is so vastly different, they get the fall like a brick as soon as you cut the power reputation, they are just much quicker in response..kind of a power to weight ratio thing?
I'd wager a beefed up version of exact external dimensions of the max at a comprable wing loading and power to weight ratio as a ga craft would fly quite similar to it
Agreed, for example, the wing loading of a 500lb gross weight minimax is 4.44lb/sqft and a cessna 172 based on a quick google is 13.5lb/sqft. a 747 has a wing loading of 134lb/sqft. I know that the ultra-efficient gliders have a very very tiny wingloading and yet they glide far, but that is because per given weight, they have much less drag then an equivalent normal aircraft.
A 747 has a coefficient of drag of 0.031, a cessna 0.032.
A 747 based on some googling has a glide ratio of 17:1, wheras the cessna has a ratio of 9:1.
I'm sure my math is completely crap and my comparisons wrong, but it feels.. okay? They have similar drag ratios, but because the wing loading is so much higher on the 747, that means that it has more momentum and wing loading and thus glides further and is harder for the air to slow down. Or its just a coincidence.
In the world of aeronatics, all wings are equal, but some wings are more equal! rotary aircraft are the most inefficient aircraft ever invented by man! I think David at team has done more for me then I can congratulate him for
Actually, what you need to consider is the Lift/Drag (L/D) ratio for the glide performance (which changes with angle of attack, flaps, etc) for each aircraft.
For slowing quickly at when reducing power, you can pair this with the familiar F=MA. With F being the drag Force, M being the aircraft mass and A being the deceleration. It will slow as A = F/M. So... the smaller the M, the larger the A. Also the large the F the larger the A for a given M. Some ultralights have very high drag (strut braces, flying wires, open cockpits etc) and some have much lower drag (like the Ultracruiser with no struts and a canopy). The lower drag bird would behave more similar to a higher mass bird by the above ratio, however this would be tempered a bit by the similar increase of induced drag due to the higher AOA on landing.
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