Flash first flight
 

Here's some pictures of my Flash's first flight (thanks Marty!). I had air problems and couldn't retract the gear on that flight. I got those fixed and was able to put them up on the next two.

I really like the looks of this plane in the air. I was very worried that it would be hard to see, but with my paint scheme, it was very visable both against blue sky, and against overcast.

As far as the flying is concerned, it was good, but I have a few issues to work out. The first was that the stock aileron sensitivity with the flaps up as too high (I set the rates up to correspond to flap setting as per the manual). That was easily fixed. I kept the higher rates on half-flaps and full-flaps but raised the expo.

It required too much forward pressure in inverted flight, so I need to remove some nose weight. I simply taped lead shot to the front of the main airbottle in the nose, so that is easily done. I also noticed a pretty good pitch-down with flaps which surprised me. I did not put in any elevator-flap mix as per the manual.

I also noted a pretty good nose-up pitch with power. When I trimmed it for level flight at full power, it would require a significant amount of back pressure for level flight at half-throttle. Has anybody noticed this? It is very prevalent with full flaps. When I roll level on final and chop the power, the nose drops big-time - requiring an immediate hard pull to avoid pancaking into the ground. I may experiment with a bit of a throttle-elevator mix, especially at full flaps, to help counteract this.

I flew quite a few laps at full power with the P-120. The airplane definately scoots at full power, but its very managable. The P-120 is plenty of power for this airplane, but its not too much as some folks have told me. I think its a perfect match for the Flash.

Bob

RE: Flash first flight
 

First off, congrats on the successful flights.

A couple of comments ...

The ailerons are very very effective on both the flash and the lightning. I dial them back a little and use lots of expo. They are very quick, but very precise.

The pitch change with flaps is to be expected. The flaps are not pitch neutral.

The pitch change with power is unusual. I would remove the nose weight, which is likely a contributing factor, and see if the problem persists. You did not mention it, but if the plane is nose heavy it probably also had a tendency to drop the nose in level turns, as well as when inverted.

Thrust line could also cause this problem, but it is pretty hard not to get the proper thrust line in this model assuming you built without modification and made sure the engine was centered in the bypass.

If you PM me with your email address, I will send you a spreadsheet with weight and balance calculations for the one I built.

RE: Flash first flight
 

Keith,

The issue with the pitch change with flaps is that the manual calls for nose DOWN trim with flaps (which I did not yet mix in, luckly), and my plane needs nose UP trim with flaps.

Again, this may be due to my CG being a bit forward, but its not really that far forward. The forward limit is 370 and I'd guess that I'm no more than 375. Like I said, I'm going to remove about 2 oz. of lead at a time from the nose to see how it goes (I have 6 oz. total up there). I'm also going to setup the throttle-elevator mix with very small corrections to start and dial it in.

Bob

RE: Flash first flight
 

Bob, the up trim is normal when you deploy flaps. On my 10x, I have 12 units of up trim mixed with flap deployment.

Do you have access to a baby or package scale? If you can get me a weight from each of the three wheels I can do a precise comparison of CG. You just need to block up the wheels you are not weighing so the plane is level when you take the weights.

RE: Flash first flight
 

Keith,

The only reason I am debating with you on the flaps issue is that the manual implies that the aircraft will nose UP with flap deployment and requires nose DOWN trim. This is normal for most of the jets I have flown, both my own and the ones I've flown for NASA. I am glad you've seen the same thing as I with your Flash (nose DOWN with flaps requiring nose UP trim), but I wonder why the manual is wrong...

If its OK, I'll send you a PM for the spreadsheet. The guys I work with at NASA also use the weight-on-wheels method to calculate CG and I know its more accurate. I'll get the weight on each wheel of the Flash after I break it out, remove some nose weight, and assemble it again. That probably won't be for a couple of days as I have some chores to do and have to get back to work soon... :(

Thanks!
Bob

RE: Flash first flight
 

Hi Keith

I read your weight on wheels method with interest, I used to be involved car racing when we did corner weights.

As my models are larger than the two fingers method I was wondering if you would be prepared to send me your spreadsheet, It will be for my use only! currently I suspend the model and use a plumb bob to get the c of g. I would prefer a method that is calculated from known weights

No offense taken if you want to not send the sheet

Thanks Ian

RE: Flash first flight
 

Sent you the spreadsheet. If you have questions, let me know. It would be best to get an intial reading on weights before you make any changes, just so we have a baseline history to gauge the impact of changes. The spreadsheet will actually tell you how much weight you need to remove to achieve either the factory or my balance point once you enter the initial data.

RE: Flash first flight
 

Keith

Is this spreadsheet "model specific" or can it be used on any airframe?

Very interesting idea!

RE: Flash first flight
 

Send me your email address via PM and I will ship a copy off to you, no problem. It may need a little explanation, and I'd be happy to answer any questions you have once you get it.

I bought three baby scales at the local Babies R Us for a relatively modest investment and it makes doing W&B a breeze on heavy airplanes. I am starting a collection of data sheets for various aircraft.