Hello,

I have a Giant Scale Planes (GSP) Spitfire with a Saito 100. The plane generally flies very well and is solid and smooth at high and medium speeds. The plane, however, becomes extremely sensitive to elevator deflection with both the gear and flaps down, making it difficult to land. It is very difficult to keep it from "porpoising". The cg is set so that on a 45 degree inverted upline, the plane will arc moderately towards the canopy. Is this behavior typical of spitfires? Any suggestions for reducing the sensitivity or at least how to better handle this on landings?

As an aside, I just installed the G2 flight simulator and notice that the simulator spitfire exhibits some of the same tendencies, although perhaps not to the same degree.

Thanks,

Travis

your CofG is too far back, Spits are as a rule very sensitive to elevator and this is compounded if the CofG is set too far back. I set mine initialy to where it was suggested but had to add lead to the nose to stop mine from porpoising on finals.

Add a little and try it, you will soon learn how much is enough through trial and error.

cheers
Peter

Blumax Ok so you have problems on landing, peter is correct check your c of g, but also how are your flaps deployed if you have them, if you do, check they are deploying at 85 degrees this will make the landing smoother and stop the aircraft floating on landing remember the flaps are mainly speed brakes on my 1/3 spit I only had the flaps deploying at 35 degrees and this caused all sorts of problems until I put them at 85 degrees anyway good luck.

Todd

From what you describe, it seems to me that the problem is lack of elevator authority in the landing phase since a aft CG would be very apparent in normal flight. In the real airplane the CG moves forward when the gear is deployed and this would also agravate the lack od elevator. Another factor is that the flaps blank airflow over the elevator. I used to have a problem during flare with flaps down until I start using full rate on the elevators as soon as I set up the landing. HOpefully this will help.
JG
http://mywebpage.netscape.com/warbirdscale/

JGRC love that spit of yours, how many flights has it had, great paint scheme.

Todd

Thanks for all the suggestions. I will experiment and report back with what I find out.

Travis

Spits are a little different to other wiarbirds when it comes to CofG and the elevator, get the CG wrong and you will have a nasty aircraft when landing, normal flight they are fine.

Mine flew wonderful from 1/3 to full power but on landing it was a bloody flipper till I added in the nose weight

cheers
Peter

Todd,
about 120 flights I think.
JG

What kind of retracts are you using in this GSP spitfire? Going to get the same plane and cannot get a definitive recommendation as to retracts for it. Eventually I like to get a spit like JGrc's, but the GSP will have to do as a test platform.

I suppose pneumatic (air) retracts are the only way to go for this size plane. What are all the components I will need to purchase to install the retracts? Can any of the retract components that come with the kit be used?

Thanks for the info. Trying to get my next build planned out.

p.s. Jose are you suggesting the Spit (in general) requires MORE elevator throw when the flaps are deployed?? This seems contrary to what I would think as a beginner. Good piece of information to know if I understand you correctly.

Hello Hgiles,

I am using Spring Air retracts (sorry I don't recall which model and can't find any documentation) with Robart robostruts. Richard L on these boards had this plane with I believe custom Century Jet retracts that he liked. My understanding is that 60-sized mechanical retracts will not work well with this plane because of the weight.

I did not use any of the retract components that came with the plane and I don't know that you could, if you use air retracts.

When the flaps are deployed on my spit with the gear down, it's not that it requires more elevator throw, it's that the plane becomes very sensitive to elevator deflection, similar to what happens when the cg is moved aft.

Overall, the plane flys very well and looks great. It is not perfectly scale, but it is my first warbird and is fine in that respect for me. It has just been difficult for me to land.

Travis

Hgiles,
That's correct, in most airplanes when you lower more than 40º of flaps, the horizontal stab doesn't get enough airflow to be effective. It aggravates if you have a heavy nose airplane. In my airplane at least, I would not be able to raise the nose for flair in half rate mode unless I come much faster than necesary. Also we have to remember than not Spitfires models are the same or have being built the same way, so is hard to make a "general" rule.
Peter,
what do you mean by "porpoising on finals"?

JG

I have had a 60 size pica spitfire with retracts and it was a nice flying plane but i had to fly it with just a touch of down elavator trim to make it fly straight and level , and it took very little elevator through to fly it . too much through will cause you to high speed stall . If i set the elevator level the plane wanted to climb , so i flew it with some down trim . I now have the PICA 88INCH SPITFIRE and am finding the same charcaristics with it . I am flying it with a little down trim . I havent used the flps yet because the plane has a lot of lift with the big wing , but i will use them on the next flite . I also had to cut the elevator through down on it . Hope this helps Tom

Bluemax, how is the spit going, I may be able to help you with a video, a friend of mine video taped my 1/3 spit on finals and with the flaps down, on a long approach, with the throttle at below half. came in for a gentle landing. have a question for the other fellas why is it that when the flaps are used it alters the elevator response, does not affect mine, remember also the flaps are mainly speed brakes and do not make the aircraft alter its flight chararistics when deployed, maybe I am wrong here and each model has its own temprement.

Todd

Appreciate the responses on the retracts, now I am trying to find the best price on them for comparison. Seems I can do Robart, Spring Air, or Century Jet or any combination. Should I go to the manufacturer or try to get them through a distributor? (Tower).

Out of curiosity, would these be the same retracts I would use on a larger Spitfire (BT 83"). How do I ask for what I want -- by plane or by model number (which I don't know).

Thanks

Hello Hgiles,

I notice that many of the retract manufacturers sell retract sets specifically designed for some popular kits. These retract kits are already sized for the particular model and allegedly "drop in". For example, Robart sells a set of retracts for the large Topflight P-51 ARF that are specifically designed for this plane. I would personally give strong consideration to one of these pre-made sets, but others may use a particular brand that they like, even if a specific set is not necessarily available for a model. For example, some people like the idea of using Spring Air retracts because they will come down if there is an air leak or otherwise insufficient air pressure in the system. Others do not feel that the "spring down" feature is a deciding factor for them.

I have not found a set of air retracts that are specifically made for the GSP Spitfire. Assuming one does not exist, then one option is to send a set of plans with measurements to a manufacturer and have a custom set made. See Richard L's set made by Century Jet. Another option is to purchase a set of retracts and cut them to fit, e.g., Robarts with robostruts.

One note about the GSP spitfire is that the mounting beams and the wheel well are positioned so that the landing gear need to have a bend to fit. This made the installation more difficult for me. Take a look at the bottom of the wing and you will see what I mean.

Travis

I have both a 1/5th scale Hurricane and a 1/5th scale Spitfire. The Spitfires flaps are much smaller, relatively speaking, than the Hurricane. When deploying the Spits flaps (to 85 degrees), the plane lands beautifully. When deploying the Hurricanes flaps to 85 degrees, the landing flare disappears. The flaps are much larger and the tailplane of the Hurricane is smaller than the Spitfire. The blanking of airflow over the surfaces appears to affect the Hurricane much more than the Spitfire. Don't think this was the case with the full size fighters, however, so it seems to be related to the scaling factor

LAFlier,
Is hard sometimes to make a general rule on specific models, since they all built different. Weight/wing loading may also affect the way they react when putting flaps??
jG

Jgrc, I agree trial and error.

Todd

Hi Heywood; What scale is that Spit? I have been custom building gear for about 28 years and have done many Spits. A few years back, PICA must have had a fire sale on kits, because I built something like 16 or 17 sets for that kit! One day I was working on one and got a phone call. "Do you build gear for the Pica Spit?" While talking to him, I got a call-waiting beep, so put him on hold. "Do you make a gear for the PICA Spit----!! So I was building one and talking to 2 guys about the same thing! By the way, The cg on some early Pica Spit plans was wrong! It made for one squirely plane!! Lee Robinson W. Palm Bch, FL [email protected]

I had the same problem with my GSP spit, it really was a lousy plane to land. The flaps are killing the flow over the tail for sure. It was tough trying to land on grass without the flaps due to the higher speed. The rudder coupling was one of the worst I've ever had with a warbird too. I'm sorry to say, I really loathed that thing. The GSP FW190 seems to be the best of their bunch. It lands just like a higher loaded warbird should.

Since the flaps on this thing are not scale, I would imagine those with the scale split type would handle different. The spit in it's full size form was not known for greased landings. I went to Duxford in 2000 and saw 20+ fly. Plenty of bumps-a-daisies when they were coming in. I have a yellow spit ready to construct and I have heard it's a real dream to land. It has more scale like flaps, coincidence ?

S1

Ok folks a change of subject, I am after a set of plans to make my own retracts for a 1/4 scale spit. any help appreciated.

Todd

Good morning Haywood; I can't remember if I mentioned price on my Spit gear, 1/5 scale. They are $300.00 shipped. The mechanics are only 1-1/4" high, and I believe would fit both planes. When I get the dwg info from you, I'll be able to tell you exactly how they would work. In a couple of weeks, after I get all these Bearcat sets out, I'll be starting a new run and still have a couple of slots open. Sincerely; Lee Robinson W. Palm Bch, FL