Topic Author
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Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 12:12 am

Many aeronautical books, state that the historical Dec 17, 1903 Wright Bros´ flight was the first SUSTAINED powered flight.

The data we are given is that the aircraft weighed about 840 pounds, and that the engine produced about 12 HP, that they used a catapult to assist the take off, that they had pretty efficient propellers (then) and that they were flying into a plus 25 mph wind in front of some sand dunes. We are also told that the aircraft´s stall speed was in the order of 32 mph.
I am not an aeronautical engineer, but I have read that a practical way to estimate the power requirements for sustained flight is to divide the aircraft´s weight by its L/D (at that speed).
An esay way to measure
Now, if you look at the aircraft, it is not as refined as, say, a QuickSilver ultralight (2 wings instead of one, many more wires and struts, but on the other hand, a pilot prone position, instead of a seating position). The Quicksilvers best L/D (glide ratio) does not exceed 5 to 1.
950 pounds (aircraft plus pilot) into, say, 5 = 190 pounds of thrust required to sustain level flight.
A very good UL prop over 64 inches in diameter that does not turn more than 2,500 rpms will produce about 5 lbs per HP of static thrust.
So, using these numbers the power requirement would be at least 195/5 = 39 HP.
The best ultralight single seaters designed for minimum power requirements need at least 25 HP aprox to keep aloft.
Granted that ground effect if flown very close to the ground would reduce the power required considerably.
No matter what reasonable propeller or aerodynamic efficiency we consider the power gap is too big to consider that historic flight as truly "sustainable"
No wonder, all true replicas built on the anniversary never flew off the rails.
The only ones to fly had a Harley Davidson 83 HP engine on.

I ask myself (and you):

Wasn´t that historic flight (recorded by cameras and witnesses) really a slope soaring flight taking advantage of those very high winds ?

Can anybody "straighten" my numbers ?

I could be wrong...
Jaime Sada
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 12:47 am

I didn't check your numbers, but I think you've answered your own question. You state that a UL prop will produce 5lbs per HP of static thrust. Statically, the Wright engine could not provide enough HP so the Wright brothers required an assisted takeoff. Propellers provide more thrust per HP as airspeed increases. As the Wright flyer accelerated down the launch, the engine was able to produce more and more thrust per HP.
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 1:36 am

L/D: ~10
Weight: 420 * 9.82 N = 4120 N
TAS: 16 m/s

Drag = 412 N
Power required: 412 * 16 Nm/s = 6600 Nm/s = 8.8 hp

If the engine put out 12 bhp, this means the prop efficiency would have had to be 8.8/12 = .73.


The big difference is of course the assumed glide ratio (L/D), but I do belive that 5 is way too low. Long wings, no junk such as a pilot hanging out in the slipstream...

I thought I was doing good trying to avoid those airport hotels... and look at me now.
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 1:38 am

No need to check your numbers, I can answer the other part of your question.

NO, it was not a slope soaring flight.

There was no appreciable slope. No upslope wind, no mechanical lifting.

Kill Devil Hill, where they had accomplished other slope soaring glider flight lies at some distance to the place where they performed the famous "first" flight. It took advantage of the steady onshore wind characteristic of the outer banks but that only had the effect of giving them free airflow while in contact with the rail. They still had to use their engine power plus an insignificant amount of catapult thrust to accelerate against that wind. It also had the effect of shortening the distance flown per time aloft.

There are so many variables at play here that the failure of any given attempt to replicate proves exactly nothing. No one else has proved that they could have flown by flying on videotape. Well so what? As the saying goes, absence of evidence is not evidence of absence. It proves nothing.

One thing cannot be disputed. The B-747, Concorde, the Space Shuttle, Bert Rutan's airplanes, and even modern helicopters all have one thing in common. The engineering in them is part of an unbroken chain of data that leads inevitably straight back to the Wright brothers and their work at Dayton and Kittyhawk. It does not lead to Santos-Dumont or any other claimant to the first-flight honors. Only the color of aviation history leads to these worthy persons.

When straighening the numbers, please include modern dynamometer data from the actual engine using fuel identical to that used on that day, and moisture content of the wooden structure of the plane on that day which might affect its actual weight. When we have that I have a few more variables to consider.

Jsada I don't mean to offend you over this but it is something we on this forum have seen many times - attempting to use numbers to disprove that something that actually DID happen.

As I see that you are new to aDOTn may I be the first to say bienvenidos. May I also be the first to say this. There is a Search function here. This topic was beaten up back in December around the time of the centennial of the flight.

Again, welcome, enjoy your time here.

no hablo Espanol - ni una palabra

Happiness is not seeing another trite Ste. Maarten photo all week long.
Topic Author
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 1:57 am

Slam: Clarifications:

1.- I am not attempting to use numbers to prove or disprove anything. My objective is to learn more, to improve on what I have already learned. As you say, the evidence is there, that it did happen and there is no question about the world wide importance of the event and the advance in the technology.
The question really is: How can we best explain it, with our aerodynamic knowledge.

2.- Yes I a a newcomer and i tried the search function with keywords such as "Wright" , "December 17 1903" and "Kitty Hawk" with no luck. I was surprised to see no results. Obviously, by your reply, I do not know how to do it properly. I will now look for those posts again, but FredT just gave me some new mathematically insight. L/D = 10 due to the prone position ? Mmm....that´s on par with a Cessna 210 or a hang glider with prone position
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 2:35 am

Why make all those estimations?


see the "power required" section.

>No wonder, all true replicas built on the anniversary never flew off the rails.
I knew this would happen.. non-engineers making judgements about 1903 based on 2003.
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Wed Apr 21, 2004 7:10 am

Check out this decent webpage...it's not exactly what you were wondering about, but could provide insight in some form or another...

As for the calculations, Fred, spot on! The only unsure aspect is what the actual L/D ratio was, and judging by the link above, it could have ranged from as low as 3 (though that low is unlikely in terms of the actual flight, I'd say) to as high as 15. 10 seems fine for estimating, though...

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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Thu Apr 22, 2004 7:11 am

Fred definitely gives us the best numbers. I wouldn't be surprises to learn that the best L/D is in fact a little better than 10, maybe 11-12-13?

Compared to other early flight pioneers the Wright bros. used a surprisingly efficient wing airfoil section which they had developed in their own wind tunnel.

Also remember, on 17th December 1903 they didn't make just one flight, but several flights. The last one lasted about one minute and covered quite some distance. Anybody who have seen just pictures of the venue will know that no noticeable slope effect could have played a major role in that successful flight.

Another thing, they didn't stop there. They developed the plane and improved the engine. And then they climbed to altitude, even with a passenger.

So the answer is no. There is no reason to doubt that the Wright bros. on that famous day made a sustained, powered and controlled flight.
Always keep your number of landings equal to your number of take-offs
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RE: Wright Brothers´ Historic Flight Dec 17, 1903

Thu Apr 22, 2004 8:53 am

While I do not have any references in front of me, I remember from the TV documentaries that the replica engine produced 16hp when connected Ford's dynometer.


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