Another Flying Flea question

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rtfm

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Hi,
I have been corresponding with a Flea afficianado here in QLD Australia. He lives about 2 hours from me, but so far, we haven't met. However, he has strongly criticised my contention that a Flea should have (at most) -1 deg negative pitch, and a max of +12 deg. Most Fleas for which I have plans (HM290, HM293, HM360) stipulate a pitch rqange of zero to +12 deg.

However, my guy says the following:
Why do you have so little down pitch on the front wing?? I have never flown a flea with so little dwn pitch it is very dangerous if you have an engine out on take off. The HM1000 I have a lot of hours on has 12 positif and 12 negatif ,.May I suggest you allow for that much movement on the flea bike to save someone's life .I have had EFATO several times and only got safely down by having that large down pitch .Please for the well being of the pilot and the reputation of the fleas make the changes ,now! This is extremely critical on tricycles more so then on tailwheelers .
I am completely confused by this. Every set of plans to which I have access stipulates zero negative pitch on the front wing. For example:

1595661578159.png
Can anyone shed some light on this?

Regards,
Duncan
 

Victor Bravo

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I can't speak from any formal/technical qualifications, but if you have too much nose-down control power from the larger main (forward) wing, it might rotate the aircraft briskly enough that the smaller (rear) wing has an inverted stall. If that happens, it's not out of the question that the aircraft would do a forward somersault of sorts. In that event, the inconvenience of bailing out of a Flea (between the wings) might become rather unpleasant.
 

Tiger Tim

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This statement is kind of suspect:
This is extremely critical on tricycles more so then on tailwheelers .
Why would the principles of aerodynamics care where the wheels were on an airplane in flight?
 

TFF

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It sounds like it’s a reference point problem. I imagine you are talking aerodynamic and he is talking control stick movements. No matter whAt, a two hour drive to see his craft an absorb what it is , would be worth a year of corespondents; agree or disagree on application. In action would be treat too.

First if he does have negative AOA available, he has leverage so the negative lock effect can be broken, or he is dam lucky. Lucky because whatever he did different works or he is just lucky. Blind luck happens. If you don’t go face to face with him and his craft, you are guessing at his luck. That means you have to be double lucky to interpret his words and ideas correctly, odds wise. That is betting on too much luck.

For one with an experimental aircraft, that a design is as vetted as much as you want it to be by the builder is not always true. They built what they wanted be dam of technical or reasonable. It is experimental for a reason. Data only has to pass regulatory requirements. Yes they may be risking their life, but it’s their choice of what is a reasonable risk. There is always a movement to unflea a flea. That has varied success, usually not. Don’t assume someone else cares about the engineering as much as you.
 

rtfm

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Hi guys,
He is definitely referring to the incidence of the front wing. Relative to the reference line of the plane (top longeron).

I've read just about everything written about the Flea, and I have never come across this before. But I'll go through my references again, just to be sure. I don't want to make a cock-up just because I'm too proud to make a change.

Duncan
 

TFF

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I imagine this guy did not want the stall protection of the regular Flea design and wanted it to handle like a regular airplane. A lot of regular pilots don’t like flying Ercoupes. A regular Flea and a regular pilot will not be happy either. I bet his CG is not where a normal Flea is.
 
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I would find that piece of advice questionable in the extreme. It's counter to everything I have heard and read about the Flea, from the 1930s to today. I know the fellow you mean, at least somewhat, and I'm sure he's knowledgeable, but I would not be comfortable following this piece of his advice. It is simply begging for you to run into an uncontrollable pitch-down situation like the early fleas.

He is definitely referring to the incidence of the front wing. Relative to the reference line of the plane (top longeron).
 

rtfm

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The developing story:
In response to my asking why down pitch was required, I received this answer:
In an EFATO if you cannot bring the nose down FAST you may be history , more so if you are close to the deck. PLEASE listen to me and go to + and -12 on the front wing. A flea will take off at +1 degree so how are you going to stop it pitching up too far and go inverted? On a nose wheeler the down pitch acts as a brake as well very good in high winds or short strips
I'm not sure I understand his comment about the plane pitching up on an EFATO. Likewise his final sentence.

Duncan
 
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Vigilant1

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Likewise his final sentence.
I interpret the last sentence to mean that, with a trigear, after touchdown the front wing could be pitched down to -12 deg providing aerodynamic drag and some stopping force.
I suppose. I can't believe it would generate much drag at flea speeds, and a retarding force ahead of the CG would not be a stabilizing one.
 
Last edited:

plncraze

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Stanton said in "Design of the Aeroplane" that when he landed his first tail dragged Flea he stomped on the brakes with the stick all the way back and got a big surprise. The tail came up quick!
 

rtfm

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Hi,
I think, on balance, that the consensus is to keep negative pivot to a minimum. I'm using the F5Fras15 airfoil, which has zero lift at -3 deg. So I'm limiting my negative pivot to -2 deg.

On a more "positive" note, there is a Fly-in about three hours from where I live this weekend. There will be three Fleas in attendance, plus my correspondent. I think I'll make the trip and see/speak first hand.

Regards,
Duncan
 

Gary Hogue

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Hi,
I have been corresponding with a Flea afficianado here in QLD Australia. He lives about 2 hours from me, but so far, we haven't met. However, he has strongly criticised my contention that a Flea should have (at most) -1 deg negative pitch, and a max of +12 deg. Most Fleas for which I have plans (HM290, HM293, HM360) stipulate a pitch rqange of zero to +12 deg.

However, my guy says the following:


I am completely confused by this. Every set of plans to which I have access stipulates zero negative pitch on the front wing. For example:

View attachment 99500
Can anyone shed some light on this?

Regards,
Duncan
Paul Pontois and many others have definitely emphasized the importance of no negative front wing angle. However, the HM-1000 Balerit you reference may be quite a different beast from the others you've cited. It's a two-seater and a pusher for starters. That may have a significant influence on the front wing incidence angle. A bit more about the HM-1000 here.
 
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