Author Topic: Removing outboard interceptors  (Read 1047 times)

tmcnamara

Removing outboard interceptors
« on: December 13, 2019, 03:18:07 PM »
Hi all,
What was the authorization for removing the outboard interceptors and where would I find the procedure? I noticed on mine the original slots are wide open and wondered if they are supposed to have had a cover (plate etc) riveted over them.

Best regards,
Tim McNamara MD
H391b Ser No 028 N12620

Doug Johnson

Re: Removing outboard interceptors
« Reply #1 on: December 14, 2019, 02:29:32 AM »
Tim, The interceptors were removed under Helio mod #29 I can't seem to find a copy of the mod itself or a 337 that shows the removal.

It appears that covering the unused slot wasn't part of the mod because I found this 337 on c/n 044 referring to Helio mod #29 and the covering of the unused slot.

Does anyone have a copy of Helio Mod #29 or any of the other Helio mods. I have incomplete copies of Helio mod #45 and #48

« Last Edit: December 14, 2019, 02:37:28 AM by Doug Johnson »
Doug

jmetzler

Re: Removing outboard interceptors
« Reply #2 on: December 14, 2019, 12:05:12 PM »
I might have Mod 29 at the office. I do know that SN 001 never had the unused slat opening closed over.

tmcnamara

Re: Removing outboard interceptors
« Reply #3 on: December 14, 2019, 09:58:10 PM »
Thanks Doug and Jim,

I would love to have a copy of Mod 29 (or any others that you may have Jim. I'll gladly pay you for them and for your time and efforts.)

I'm still fascinated by these planes!   :)

Best Regards,
Tim Mc

dtreid

Re: Removing outboard interceptors
« Reply #4 on: December 14, 2019, 10:23:36 PM »
FIYZ still has that slot open as well.

Jason Stephens

Re: Removing outboard interceptors
« Reply #5 on: December 15, 2019, 11:36:31 AM »
Just curious, what was the reasoning behind removing some of the interceptor blades?

Jason

Neil

Re: Removing outboard interceptors
« Reply #6 on: December 15, 2019, 01:01:33 PM »
Hello Mr Metzler, Yes I remember at the time I owned #001 the outboard interceptors opening on the wing is still open and I have the same question at this time.

Neil
« Last Edit: December 15, 2019, 01:05:54 PM by Neil »

Doug Johnson

Re: Removing outboard interceptors
« Reply #7 on: December 16, 2019, 09:35:05 AM »
This is what Louis said when this same question was asked back in 2011

Anyway, like you told me this afternoon, why putting an interceptor in front of the aileron ?  The disrupted air would probably make the aileron less effective.

I remember Larry saying that they removed it because it was giving nothing.  The interceptor are great because they work very strongly taking all the energy of a forward movement.  But they do cause a lot of drag.  Aileron do their work with a smaller drag.  I would not put interceptors in front of them.

Louis


My reply was, I can see that it would be just extra weight with no benefit and I agree, it probably would make the ailerons less effective, and Frise ailerons already protrude below the wing to add drag .

I also found the statement below is supposed to be in the log if you have a 391 with the extra slots and it had blades in front of the ailerons when the outboard interceptor are removed.

Aircraft modified, with removal of two outboard interceptor blades in each wing (Service Modification #29; Factory Drawing SK-516)
Doug

Jason Stephens

Re: Removing outboard interceptors
« Reply #8 on: December 16, 2019, 01:06:25 PM »
Interesting.  Well, if somebody needs an excuse to go flying maybe some data can be collected by video of a simple 45 to 45 to 45 kind of exercise.  By comparing the two interceptor setups we can get an idea of what is the real deal.

Jason

Doug Johnson

Re: Removing outboard interceptors
« Reply #9 on: December 16, 2019, 02:15:11 PM »
I don't think there is an H-391 still in existence that still has outboard interceptors and since it was a factory recommended removal, I suspect it would be difficult to persuade someone to reinstall them.
Doug

jmetzler

Re: Removing outboard interceptors
« Reply #10 on: December 17, 2019, 11:16:54 AM »
I do not have a copy of the mod to remove the interceptors. It is not part of any Service Bulletin as I just paged through all of them. Sorry. Jim Metzler