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PacoMartin
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Posts: 140
Joined: Sun May 27, 2018 8:18 pm

fuselage strakes

Tue Jul 16, 2019 9:24 am

https://en.wikipedia.org/wiki/Strake_(aeronautics)
https://www.law.cornell.edu/cfr/text/14/25.173

An avionic design engineer commented that the MAX engineers could have designed fuselage strakes to comply with CFR.14.25.173 . Instead they designed MCAS which he called a kludge.

Does anyone agree or have comments?
 
mxaxai
Posts: 1067
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Re: fuselage strakes

Tue Jul 16, 2019 10:02 am

Of course they could have. It would have added weight and drag but strakes do work quite well. Boeing could also have enlarged the elevator, although that would require more development and certification effort than just some simple strakes.
 
asdf
Posts: 304
Joined: Tue Mar 18, 2014 12:03 am

Re: fuselage strakes

Tue Jul 16, 2019 10:11 am

this kills the economy of that bird pretty well

they wont come near to the NEO aerea with that kind of attachment
 
B777LRF
Posts: 2421
Joined: Sun Nov 02, 2008 4:23 am

Re: fuselage strakes

Tue Jul 16, 2019 10:11 am

They could have employed any number of aerodynamic or structural fixes to the problem of mounting the new motors, some of which would have reduced fuel efficiency but almost all would have resulted in changes jeopardising the common type rating. The consequences of such actions have been debated ad nauseam on these pages and in news publications around the world, and the reasons why Boeing chose to go with MCAS instead have been solidly established.
Signature. You just read one.
 
mxaxai
Posts: 1067
Joined: Sat Jun 18, 2016 7:29 am

Re: fuselage strakes

Tue Jul 16, 2019 10:53 am

B777LRF wrote:
almost all would have resulted in changes jeopardising the common type rating.

Strakes definitely do not threaten a common type rating. Just look how many aircraft variants feature strakes that were not present on the original model. The 737 is one of them - the Jurassic does not have the dorsal fin that the later models feature.
 
GalaxyFlyer
Posts: 3349
Joined: Fri Jan 01, 2016 4:44 am

Re: fuselage strakes

Tue Jul 16, 2019 2:17 pm

Look at current Learjet, that’s why they have them. Pretty careful handling at the stall.
 
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Starlionblue
Posts: 19314
Joined: Fri Feb 27, 2004 9:54 pm

Re: fuselage strakes

Tue Jul 16, 2019 4:07 pm

mxaxai wrote:
B777LRF wrote:
almost all would have resulted in changes jeopardising the common type rating.

Strakes definitely do not threaten a common type rating. Just look how many aircraft variants feature strakes that were not present on the original model. The 737 is one of them - the Jurassic does not have the dorsal fin that the later models feature.


Quite right. However a much enlarged elevator might have meant a different rating if it significantly impacted control characteristics.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
B777LRF
Posts: 2421
Joined: Sun Nov 02, 2008 4:23 am

Re: fuselage strakes

Tue Jul 16, 2019 7:34 pm

mxaxai wrote:
B777LRF wrote:
almost all would have resulted in changes jeopardising the common type rating.

Strakes definitely do not threaten a common type rating. Just look how many aircraft variants feature strakes that were not present on the original model. The 737 is one of them - the Jurassic does not have the dorsal fin that the later models feature.


The leading word in that sentence was ¨but¨, which you conveniently forgot to include in your quote. Strakes might have done the job, albeit with the already limited rotation angle I somehow doubt it'd work. They would have come with a drag and fuel penalty though, as well as the necessary structural- and production changes and the certification of both.

Couple of lines of software, well hidden, misidentified, incorrectly assessed and kept from the customers must have sounded much cheaper.
Signature. You just read one.
 
Max Q
Posts: 7543
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Re: fuselage strakes

Wed Jul 17, 2019 12:55 am

Strikes always seem like a very inefficient and ugly solution to aerodynamic shortfalls, same with ventral vertical fin extensions

An electronic solution Is far more efficient, better looking and more
cost effective if done properly


That’s the key
The best contribution to safety is a competent Pilot.


Guns and the love of them by a loud minority are a malignant and deadly cancer inflicted on American society
 
GalaxyFlyer
Posts: 3349
Joined: Fri Jan 01, 2016 4:44 am

Re: fuselage strakes

Wed Jul 17, 2019 1:27 am

Max Q wrote:
Strikes always seem like a very inefficient and ugly solution to aerodynamic shortfalls, same with ventral vertical fin extensions

An electronic solution Is far more efficient, better looking and more
cost effective if done properly


That’s the key


Used all the time though. The delta fines on the Lear made some nasty characteristics become a pussy cat. The British ARB insisted on the ventral fin on the 707. The Mad Dogs have all manner of fins, strakes and fixes.


GF
 
Max Q
Posts: 7543
Joined: Wed May 09, 2001 12:40 pm

Re: fuselage strakes

Wed Jul 17, 2019 6:51 am

GalaxyFlyer wrote:
Max Q wrote:
Strikes always seem like a very inefficient and ugly solution to aerodynamic shortfalls, same with ventral vertical fin extensions

An electronic solution Is far more efficient, better looking and more
cost effective if done properly


That’s the key


Used all the time though. The delta fines on the Lear made some nasty characteristics become a pussy cat. The British ARB insisted on the ventral fin on the 707. The Mad Dogs have all manner of fins, strakes and fixes.


GF



True, however the ventral fins on the 707
were removed on later production and modified aircraft


They had a taller vertical fin and different inboard slats that allowed this



Those ventral fins on the Lear are crude
but effective



The -80 does have a few ‘add ons’ as well
although they certainly didn’t help it to fly
any better


The MD90 has one of the most unusual
aerodynamic ‘add ons’ I’ve ever seen with its engine pylon elevators
The best contribution to safety is a competent Pilot.


Guns and the love of them by a loud minority are a malignant and deadly cancer inflicted on American society

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