Spitfire flaps

Need technical help on some problem? Let us know and we will see what we can do
Arthur Fielding
Posts: 68
Joined: February 3rd, 2009, 8:18 pm
Contact:

Spitfire flaps

Postby Arthur Fielding » March 8th, 2018, 2:11 pm

Hi
Any one out there flown a Brian Talyor MK 9 spitfire 83in version built from his plans.
Getting ready to test fly mine and was wondering what to exspect trim wise when the flaps go down.
Would appreciate any info
Thanks
Arthur

Cary Bailey
Posts: 210
Joined: January 26th, 2011, 7:43 am
Location: Stoke On Trent
Contact:

Re: Spitfire flaps

Postby Cary Bailey » March 9th, 2018, 10:48 am

Arthur, most under fuselage wing configurations that have flaps have a tendency to drop the nose slightly when flaps are employed. This differs from one type to another. I fly a P51, which when flaps are deployed drops the nose by 10 degrees. On landing the full size you have to keep the airspeed right on the money so that at touchdown the nose it at the correct attitude (level and not pitched down, which you can monitor accurately) and at that airspeed is such that the tail naturally wants to slowly sit down, if you watch closely most full size P51 pilots raise the flaps under a certain speed after landing. With a model it is harder to judge that airspeed at landing, however what I do is when the wheels actually touch down I retract the flaps either partially or fully which avoids the nose down attitude, stops the nose from wanting to bury itself, avoids you wanting to feed in more elevator to lift the nose which causes you to overcompensate, the wing becomes into a flying attitude but the lack of airspeed causes it to stall. Raising the flaps in this way allows the tail back into it's normal attitude, stops you from applying unnecessary elevator, allows the tail to fall to it's normal position and then as the airspeed falls away the tail lowers down.

So I hope I have explained that so that you can watch what your Spitfire does as you apply the flaps. Try it during your test flight, at a height that is safe & that you can see the effect of the flaps on the nose attitude so you can then judge what you need to do. I do know some guys "mix" in a slight amount of up elevator when flaps are deployed, my advice is don't adopt that idea as it is a false economy especially if you get your airspeed to low, the elevator is still biting to lift the nose, the nose rises, causing the wing attitude to rise and you get an instant wing tip stall & a possible broken wing!

Cary

Phil Clark
Posts: 934
Joined: December 4th, 2008, 7:07 pm
Location: Chester-le-Street, Co Durham
Contact:

Re: Spitfire flaps

Postby Phil Clark » March 9th, 2018, 9:39 pm

........on the other hand, every single fighter I have flown over the past 20 years has pitched up a little with flaps, rather than the nose pitching down. (This has included multiple P-47's, P-51, FW 190D, Dauntless & Hurricane). Some worse than others & some are more airspeed critical than others, but it can be uncomfortable keeping the model level or in a gradual descent holding in 'down', so on certain models (my 190D especially) I mix in a little down so that I can still hold the nose where I want it juggling power & elevator and flare by pulling 'up' rather than releasing some of the down.

Each to their own, but I would echo Cary's recommendation in checking it all out on the test flight at a safe altitude without any mixing.......see what happens and depending on how controllable it is, consider mixing at a later date.

Phil

Cary Bailey
Posts: 210
Joined: January 26th, 2011, 7:43 am
Location: Stoke On Trent
Contact:

Re: Spitfire flaps

Postby Cary Bailey » March 12th, 2018, 10:56 am

Phil, that is very interesting in that your experience differs from mine, however I do bow to your vast experience as there are aircraft on your list that I have not flown.

I can only go on what aircraft I have flown and have flown in, the P51 (for instance) when flaps are extended, the centre of lift and pitching moment of the wing changes, changing the centre of lift changes the moment arm length for the tail to work over and changes the pitching moment of the wing that the tail is working against so the pitching is the plane adjusting to the new equilibrium between CG, wing centre of lift, wing pitching moment, tail moment arm and tail down force. On the P51 aircraft this change in attitude lowers the nose.

This interesting question about flaps got me thinking (as well as getting confused) as I know about the P51, so I called the guys I know who fly other warbirds, their responses were:-
P47 & Corsair, their planes pitch up when you add flaps
P40 & AT-6 (Texan) the attitude hardly changes at all

Therefore flaps that add a lot of lift, the plane will tend to pitch up more because of the new found lift at the same speed, flaps that are simple ones without slots will tend to pitch down, reflecting the drag.

Apologies if this got a little technical but I thought I had best get a clarification from the guys I know who actually fly these warbirds.
Cary

stuart knowles 1611
Posts: 146
Joined: December 27th, 2008, 11:46 am
Contact:

Re: Spitfire flaps

Postby stuart knowles 1611 » March 12th, 2018, 1:24 pm

I don't claim to have the experience of either of you guys. My experience has been that only once have I had to mix in a little elevator compensation (down) For the most part so long as the speed is allowed to decay before the flaps are deployed, no compensation has been needed. Some people see to have reservations about using flaps on models but I can't say I've ever known of a bad reaction from any. (except when only one comes down - that can be interesting :-) )

Frank Skilbeck
Posts: 13
Joined: November 1st, 2017, 9:20 am
Contact:

Re: Spitfire flaps

Postby Frank Skilbeck » March 15th, 2018, 2:10 pm

Nothing like the models above, but if your transmitter allows it then put the elevator compensation on an adjuster so you can adjust the amount of elevator mix 3 mistakes high!

Dave Wilshere
Posts: 53
Joined: October 18th, 2013, 7:55 pm
Contact:

Re: Spitfire flaps

Postby Dave Wilshere » March 18th, 2018, 5:39 pm

Split flaps are completely different again, but all the Spitfires I have flown with scale flaps, showed perfect flap trim...tiniest amount of pitch down. This is based on near scale amount of flap, it you set in the 'lift zone' with less flap it will be different. I have never used Flap/elevator compensation on a Spit as the sit is about perfect for 'roller' landings that you should start with.

Gear down/flap down will change what happens, you should never use full flap on slow pass like you might with some aircraft, so check with the gear down, flaps as much as you can get 80-85 degrees to look anywhere near right.

Arthur Fielding
Posts: 68
Joined: February 3rd, 2009, 8:18 pm
Contact:

Re: Spitfire flaps

Postby Arthur Fielding » May 12th, 2018, 7:49 pm

Hi
Back in March I requested information on the effects of the flaps on my Brian Taylor Spitfire. At the time still being built.
With the CG and control throws as per the plan, and in-between the rain shows it had its first flight today, and I am well pleased.
Dave Wilshere got it spot on with his description of what trim change to expect when full flap was deployed, basically none, the model just felt as if you had put the "hand brake " on so a bit of throttle was required to keep it coming, touch down on the main wheels was no problem with elevator to spare , I could not resist taxing it back to the pits .
Now I am going to paint it ,then recheck the Cg just encase.
Model Spitires over the years have had a lot of bad press,and this one is the first i have built since my control line days some 60 years ago.If you fancy a good build and a great flying mode give the Brian Taylor 83in Spitfire ago build it right and you will not be disapointed.
As a matter interest my last WW2 model was also designed by Brain Taylor a P47 thunder bolt and like the Spitfire shows no trim change when the flaps are deployed.
Lets hope the weather gets better soon.
Regards
Arthur

Mike Booth
Posts: 641
Joined: December 4th, 2008, 5:51 pm
Contact:

Re: Spitfire flaps

Postby Mike Booth » May 13th, 2018, 7:58 pm

Spitfire flaps down. Mandatory on every landing. Slight trim change as they go down. Once down, 86 degrees the aircraft will settle. You will NOT need any additional elevator trim added.


Return to “Technical Help required”

Who is online

Users browsing this forum: No registered users and 1 guest