Aspect Ratio and Span B737-300 Winglet

[PWMdk]

Dear all

I'm doing some calculations regarding aerodynamics of a Boeing 737-300 aircraft.

I've been able to find the aspect ratio and span of the wing for a 737-300 without winglets. Unfortunately, I can't find the same data for a wing with winglets.

Does anyone know these details for a -300 with winglets?

Thank you very much.

Best regards,
Peter

[blackmail]

Hello Pwmdk,
737-300 +winglet :span = 31.11m(non winglet : span = 28.88m). Mac = 3.41m
gross wing surface : S = 105.4m2

aspect ratio = span/mac or span2/S
I let you do the math

have a nice day
bm

[PWMdk]

Hi blackmail

Thank you for your reply.

However, when I try to calculate the aspect ratio using the numbers here: http://www.b737.org.uk/techspecsdetailed.htm I don't get the "correct" result (the number on the page).

With your data I'm getting an AR of 9.12 with winglets. Without winglets the number is supposed to be 9.16 according to b737.org.uk. When I calculate the AS without winglet using numbers from that website, I get 8.47 - quite a lot less than 9.16.

Any ideas what I'm doing wrong here?

[Guru8904]

PWMdk,

I agree with your calculations. I went to the same website and found your calculated values different from the website.
I have a very strong feeling that we are missing something; they are calculating using something more than the basic formula of AR= Span/MAC or (Span)2/area. Just to confirm my thinking, I calculated with both the above equations and found out that using span/MAC the value is actually 8.46 (as calculated by you) rather than 9.16.
I went on to calculate using (Span)2/area. Theoretically it should give the same result but I got 7.91.
This proves that these calculations on the website are based on a formula that includes something beyond the basic formulae. What? I have no idea.

[Guru8904]

Again, there is a problem with the area calculations also. As per the values given on the website, the product of span(28.88) and MAC(3.41) comes out to be 98.48 whereas the area is shown as 105.4.
We are definitely not in the know of something, some hidden unknown(to us) constant/variable value.

[Chesty Morgan]

Span is 32.11 with winglets.

[Guru8904]

Agreed. We are trying to find out what is causing the difference between our calculations and the values given on the website.

[PWMdk]

Totally agree with you guys, hence my original question. Since I can't seem to calculate the AR correctly, I'm looking for someone who simply knows the number.

I'm also thinking to give the winglet manufacturer a call...

[underfire]

seems like a lot of effort for a -300

[DaveReidUK]

The conventional way of working out the aspect ratio of a wingletted wing is to add the area of the winglets to the wing area and their length (i.e. height) to the span.

So, in effect, the winglets are considered as if they have been bent downwards to act as extensions of the wings in the same plane. The APB winglet for the 737 Classic is around 7 feet tall, so the wingspan (for the purpose of calculating AR) will be about 14 feet more than an unwingletted aircraft, i.e. a tad over 33 metres.

Obviously taking the span as the distance from tip to tip of the upright winglets will give a different figure for the wingspan and therefore a different answer for the aspect ratio.

[Amadis of Gaul]

Originally Posted by Guru8904

Agreed. We are trying to find out what is causing the difference between our calculations and the values given on the website.

Don't forget to take inflation into account.

[Snakecharma]

Out of interest, and not trying to be a smart arse here, but what possible use could you have for the data?