An interesting point…

D

Dave S.

Pre-takeoff checklist
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thetexan
Can a C172 take off at 4900 lbs (twice it’s 2450 mtow) given enough runway on a standard day?

tex
 
interesting question. if it could I'm thinking it wouldn't be able to climb very high.
 
Well, for one, your wing load would in theory be double to begin with. So additional wing loading in climb would be substantial. If the question is merely, "Given enough time and enough runway, could enough ground/airspeed be generated to sufficiently increase airflow over the wing to the point that it could lift off?" I'd have to say that there are other variables in play (engine power, amount of surface friction which would be increased by the added load, etc) but my gut says that, yes, it would be able to get off the ground. Now as far as safe flight (which you obviously didn't ask about) I'd say that's a different story.
 
The Commanche 250 that Max Conrad flew non-stop from Casablanca to Los Angeles in June 1959 has a gross weight of 3,200 pounds. He took off at 5,200 pounds (162.5%). According to eyewitness accounts he barley got off the ground in Morocco. More telling is that as much as Max enjoyed setting records he did not try to top that 7,700 mile non-stop trek. Suggesting that he may have found this to be a practical limit on a more aerodynamically clean airframe than a 172.
 
Say you can get off the ground at that weight: now your wing loading and associated aerodynamic behavior in straight-and-level flight is that of a normal (i.e. at max gross weight) 172 in a 60-degree bank turn.

If you take that 172 at twice the normal max gross weight and fly a 60-degree bank turn, the lift force created would be four times of the lift created at certified max gross weight in straight and level, meaning you would exceed the design limit load factor.

In other words: Even if you can get it off the runway, your margins for wind gusts, turns etc. are severely reduced. Basically you are eating up more than half (2.0g of your 3.8g limit load factor) just by carrying the extra weight.

- Martin
 
It would be highly dependent on the aircraft being used. Some types have trouble getting out of their own way at max gross (I've flown a couple of tired Warriors over the years that would qualify), while others (like the Comanche 250) have no trouble at max gross or beyond.
 
It might hop in the air a few feet before it gets out of ground effect and stalls. If you're unlucky enough to gain a 100 or so feet then when it bounces back down would be called "crash".

I suppose if "given enough runway" means 500 miles or so long, then it could get aloft and stay in ground effect until you burn off enough fuel to get below max gross take off weight.

Assume also that your CG is not out of whack with all of this extra weight.
 
Re: Consolodated's PB5Y "Catalina," 2,400 max hp, 35,420 lb gross, 20,910 lb empty, 14,510 lb useful, 1,750 us gal / 10,500 lb max fuel load.

"Another Cat needed a three-mile takeoff run to lift a total of 63" (63 x 170 = 10,710), "including its own crew, and the pounding probably popped half the rivets in the hull. But the record goes to the Australian Catalina that carried 87" (87 x 170 = 14,790) "Dutch sailors — standing room only, thank you — after Japanese bombers mauled their freighter."
(Navy Times Aug 2019)
 
Imagine trying to take off in a Cessna 207 (GW 3800#) with only 150 HP (1/2 power). Both the 172 and the 207 share the same wing area. The OP’s suggestion of a 172 trying to take off @ 4900# would be quite a feat.
 
Guess I'm the only one that wants to know...Why?
 
Brad Smith said:
Imagine trying to take off in a Cessna 207 (GW 3800#) with only 150 HP (1/2 power). Both the 172 and the 207 share the same wing area. The OP’s suggestion of a 172 trying to take off @ 4900# would be quite a feat.
Click to expand...
Ah, a testable hypothesis. I would suggest 8 / 26 at BQN (Aquadilla, PR), built for B-36s the 11700 runway has about 3 miles of pavement including displaced thresholds at each end.
 
Well, we know it will fly at a wing loading of 2.0 since it will do a 60 degree steep turn.

As has been stated you are already at a significant fraction of the structural limits so it won’t tolerate much more. I guess it would depend if you could get out of ground effect.

tex
 
If you departed sea level and if the altimeter was >30.00, and if the temperature was -7F and if you could load the 172 so it had a CG that allowed for the aircraft to be controllable, the plane would probably fly.

DA at my scenario is well below sea level.
 
Is it on a treadmill?


(Sorry, someone had to say it…)
 
Warren Dunes said:
Ah, a testable hypothesis. I would suggest 8 / 26 at BQN (Aquadilla, PR), built for B-36s the 11700 runway has about 3 miles of pavement including displaced thresholds at each end.
Click to expand...
I never knew the Bonanza was such a runway hog :devil:
 
Dave S. said:
Can a C172 take off at 4900 lbs (twice it’s 2450 mtow) given enough runway on a standard day?

tex
Click to expand...

Taking an optimistic mathematical approach, it would take twice as long to accelerate, and four times as much runway length. If you add in increased tire friction due to weight, you would probably need about 5-6 times the runway length.
 
midwestpa24 said:
If you sneeze out the window facing rearward, does the sneeze create additional thrust?
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Yes, of course. Somewhat less than the additional drag caused by the open window and your head sticking out.
 
Throwing things out out a ship is an old practice. The apostle Paul was on an ocean journey where they threw everything they could overboard to lighten the ship. Same practice on bombers in WWII. Didn’t help Paul, not sure about those bomber crews.
 
Brad Smith said:
Throwing things out out a ship is an old practice. The apostle Paul was on an ocean journey where they threw everything they could overboard to lighten the ship. Same practice on bombers in WWII. Didn’t help Paul, not sure about those bomber crews.
Click to expand...


Seemed to work okay for the Tarshish sailors who tossed Jonah overboard.....
 
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