Mid-wing the secret to high speed?
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Mid-wing the secret to high speed?
It seems to me that the fastest aircraft for any given power are mid-wings. Aerostar is the fastest in its class, Piaggio Avanti II is fastest in its class etc, fighters, etc. Is it because the wing box sections of all the other designs make them more draggy when they sit at top or bottom, or is there some other secret sauce present in mid-wings?
Not exactly Adam.
While the examples you cite are fast in their class, this isn't always true. In the medium piston twin class,it just happens that the Aerostar has a smaller fuselage and wing cross-sectional area than any other airplane in it's horsepower class. Less parasite drag per horsepower than other aircraft in the class coupled with some nice airflow shaping are what make Ted Smith's creation tops in it's class speed-wise. IIRC, it was originally designed with jet powerplants in mind.
Similar high speed drag considerations for the P180. The Piper Cheyenne 400LS (low wing) produced only a little less top speed but with a bit more cabin volume and superior climb performance to boot, albeit using somewhat more horsepower and prop disc area than the Avanti.
Fighters and high performance piston aerobatic planes often utilize a mid wing configuration, but quite likely due more to structural and other advantages. Notice that the fastest production and kit piston singles are low-wing? That's okay though, I quite enjoy the Cessna high wing singles myself.
High wing, low wing, mid wing, just make it a good wing!
My own piloting experience includes a bit of each, with a little more than half of it in one particular mid wing model. This particular mid wing jet model happens to be among the slower types in it's class, but has a pretty good combination of speed, range, payload and economics for a straight-wing jet design of it's vintage. When they put the same fuselage, empennage and nearly identical engines on a sleeker swept low wing, the max cruise speed was increased by at least 40 knots. Some of that is due to reduced wing profile and some to the mach induced drag reduction that comes with wing sweep.
Of course I'm describing the IAI-1124 Westwind and the IAI-1125 Astra. Before it was a Westwind it was a Jet Commander and before that a Turbo Commander. When they replaced the 731-3 engine rated at 3,700 lbs thrust with the -40 rated at 4,200 lbs, the Astra SPX could out run the Westwind by a good bit more than the earlier Astra models. In fact on a good day you can get .75 mach out of a light Westwind and .86 or better out of the SPX/G100. Drag versus thrust determines speed and total area presented to the relative wind is a big player in where the two shall meet. Smoothing the airflow around the aircraft gains importance as speed is increased too, but this can be done efficiently with high and low wings also.
I know you're looking fondly at the Aerostar Adam!
If and when you get one, respect it's low speed handling characteristics and fly it with even more care and precision than you need to in the Commander. It's a step up in performance class for sure and will demand a little more from you. I presume you'll seek a professionally administered transition course and that you've already considered this. Best of success in taking the next step.
Best regards,
westhawk
While the examples you cite are fast in their class, this isn't always true. In the medium piston twin class,it just happens that the Aerostar has a smaller fuselage and wing cross-sectional area than any other airplane in it's horsepower class. Less parasite drag per horsepower than other aircraft in the class coupled with some nice airflow shaping are what make Ted Smith's creation tops in it's class speed-wise. IIRC, it was originally designed with jet powerplants in mind.
Similar high speed drag considerations for the P180. The Piper Cheyenne 400LS (low wing) produced only a little less top speed but with a bit more cabin volume and superior climb performance to boot, albeit using somewhat more horsepower and prop disc area than the Avanti.
Fighters and high performance piston aerobatic planes often utilize a mid wing configuration, but quite likely due more to structural and other advantages. Notice that the fastest production and kit piston singles are low-wing? That's okay though, I quite enjoy the Cessna high wing singles myself.
High wing, low wing, mid wing, just make it a good wing!
My own piloting experience includes a bit of each, with a little more than half of it in one particular mid wing model. This particular mid wing jet model happens to be among the slower types in it's class, but has a pretty good combination of speed, range, payload and economics for a straight-wing jet design of it's vintage. When they put the same fuselage, empennage and nearly identical engines on a sleeker swept low wing, the max cruise speed was increased by at least 40 knots. Some of that is due to reduced wing profile and some to the mach induced drag reduction that comes with wing sweep.
Of course I'm describing the IAI-1124 Westwind and the IAI-1125 Astra. Before it was a Westwind it was a Jet Commander and before that a Turbo Commander. When they replaced the 731-3 engine rated at 3,700 lbs thrust with the -40 rated at 4,200 lbs, the Astra SPX could out run the Westwind by a good bit more than the earlier Astra models. In fact on a good day you can get .75 mach out of a light Westwind and .86 or better out of the SPX/G100. Drag versus thrust determines speed and total area presented to the relative wind is a big player in where the two shall meet. Smoothing the airflow around the aircraft gains importance as speed is increased too, but this can be done efficiently with high and low wings also.
I know you're looking fondly at the Aerostar Adam!
If and when you get one, respect it's low speed handling characteristics and fly it with even more care and precision than you need to in the Commander. It's a step up in performance class for sure and will demand a little more from you. I presume you'll seek a professionally administered transition course and that you've already considered this. Best of success in taking the next step.
Best regards,
westhawk
Last edited by westhawk; 3rd Jun 2013 at 05:22. Reason: small corrections!
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It might have something to do with the angle at which the wing meets the fuselage, right angle is usually least drag.
Also makes it easier to engineer a "waist" into the fuselage at the join, to reduce drag further by reducing the fuselage's cross section.
Also makes it easier to engineer a "waist" into the fuselage at the join, to reduce drag further by reducing the fuselage's cross section.
An area-ruled mid-wing is going to have, in theory, the least induced drag due to the fuselage acting as a "Dam", minimising span-wise flow. It also means roll is exactley about the longitudinal axis, a plus for aerobatic aircraft and fighters.
But aircraft design is a series of compromises. If, for instance, the fact that to achieve this, you have to put a spar through the middle of your fuselage, mucking up your ability to house fuel/engine/payload, and thus have to have a bigger fuselage and thus more weight and drag, you've probably negated any advantage you had to begin with.
90% of configuration decisions are structural or commercial, rather than aerodynamic. For example, Extra Aerobatic aircraft started with a mid wing. Current ones have a low wing, as it improves the pilots visibility whle having almost no actual effect on performance.
But aircraft design is a series of compromises. If, for instance, the fact that to achieve this, you have to put a spar through the middle of your fuselage, mucking up your ability to house fuel/engine/payload, and thus have to have a bigger fuselage and thus more weight and drag, you've probably negated any advantage you had to begin with.
90% of configuration decisions are structural or commercial, rather than aerodynamic. For example, Extra Aerobatic aircraft started with a mid wing. Current ones have a low wing, as it improves the pilots visibility whle having almost no actual effect on performance.
