i bought this av8r from a guy and have been having problems getting the thing off the ground. it weighs in at 19 lbs. wet once in the air it flys good, it's just trying to get it in the air that's the problem . after getting caught up in the steering whip i ran it into the tall weeds and the engine mount broke. i got the mount out of the plane and got looking at it . it looks like there is to much down trust in the engine . almost like the mount was put in back wards . if anyone has a set of plans that they could take a pic of "the engine Mount area"
i would really appreciate it. here's the orientation of the mount as it was in the plane . many thanks ,warbird_1

the down thrust in the pic looks ok to me. the turbine should point to the cg. this keeps the jet from changing pitch at different throttle settings. mine flew great with the down thrust, barry

Here's a section of the plan showing correct thrust line…

Dennis

if you look at pats prototype you'll see the engine is almost parallel to the hoz. stab . that's why i think the engine mount was put in backwards . if you turn the mount arond the engine will sit like pats does , warbird

thank you dp

DP , i just check the old mount against the pic you sent and i'm getting 8 degrees of "what they call " up thrust when it should only be 3 degrees. i wonder if that could be driving my nose into the ground when i'm tring to take -off , warbird

Ron,
i can assure you that the mount is at the correct angle....i questioned Pat at PCM Models about it.....

Richard

Warbird:

The 3º angle is measured from the fuselage datum line. Perhaps you are measuring from the fuselage top? The AV8R has no take off problems (or flight problems) with the designed thrust angle. 15º flaps for take off shortens the run.

Dennis

i'm using the elevator surface as the datum line . it should be the same . i know better than use the top hehehe

Sorry about that! The angle to the top looked about right for 8º. Out of interest, I measured the angle on my AV8R, and the precut engine pylon results in 3¼º.

Dennis

Dennis, you've got one of the best Looking AV8R's I have seen, well done.

Angus

P.S. you did'nt make it out to leamington this year?

Warbird.... I don't think it is the angle at which the turbine is causing your problem. When you think about this, If the turbine is pointing at a slight angle (front down 3 deg) it is pushing on the rear of the plane down, which in turn would cause the noise of the plane to go up at higher thrust. Just the opposite if you had the turbine thrust angle pointed up to where the front of the turbine is higher than the rear. That scenario is trying to pull the rear of the plane up and inturn push the nose of the plane down.

I would be checking the CG of that plane to see if it wasn't a lil NOSE HEAVY. Also, where is the bulk of the fuel on that plane? Is it ahead of the cg. Could it be causing a nose heavy take off. U2Fast and I experienced a real nose heavy facet this weekend that was very close to not taking off on its maiden. I think the cg was about 1-2 inches ahead of where it should have been. U2Fast was flying it with full uptrim and about 3/4 of the up elevator just to keep it flying level.

Somthing else to check would be the angle of attack that the plane sits onthe ground. Is the nose a little lower than the rear? if so... try to get level if not a slight nose high angle of attack. That should help a bunch.

jetfreak

Warbird:

I see you are using the single strut nosewheel. You might want to try the Fults dual strut unit to help maintain a straight line on the take off roll.

Angus:

Thanks! I did make it to Leamington but could only stay for the Saturday morning.

Dennis

dp , thanks for the pics . your engine is a lot closer to level than mine. i just ordered a new nose gear retract from robart. i think your right about the nose gear. i think it was wandering a lot during take-off. as far as the CG goes it's right on the backside of the CG limit. talking to eric at robart "who has a av8r" he agreed with me on that fact that because of the excess angle of the engine , the plane was being pushed into the ground . case in point. the first flight i made i was at the end of the runway full throttle , i cut the power to get stopped and as soon as the power came off the plane rotated. ...... warbird

again thanks a lot for the help you guys are offering

rich , i wasn't saying it was built wrong , just thought the angle didn't look right and that there was a CHANCE the part was put in wrong. in fact i did find that the trust angle on the part that was installed was at 7 degrees when it was supposed to be only 3 . however the part was installed right. you may have been given a bad part . anyways i'm thinking the high angle was driving the nose into the ground at high speed or high power. thanks ,warbird

DP , any chance you might know how much flap is used during take-off? thanks ,warbird

I used 10 degrees

10? why?

The PCM manual suggests about 20º (see attached). Dean Wichmann's flight notes - in the other AV8R thread suggested 15º. I went with 15º and that seems to work OK.

With the variety of apparently successful opinions regarding the takeoff setting, it's likely not too critical.

Dennis

With 15 mine didnt rotate smoothly, it kind of leap off the ground, so I used less and it was perfect

but really takeoffs are not an issue with this plane, you don't need flaps

the landings on the otherhand.....

i had no problems landing other than i needed a speed brake. i had to use a lot of airspace to bleed off speed. even though mine is heavy , it felt light on the sticks other that trying the get it into the air which most of the time took full elevator to do it . and that's with flaps half way , warbird

here's what i came up with

dp , would you happen to know how much positive incidence the fuse calls for on the plans?when it's on it's gear . i'm using the hoz. stab for my measure ment. many thanks ,warbird p.s. i found the first setup was at minus 1/2 to 1 degree of negitive incidence

The plan says "Slightly nose down" - looks like about 1º or so.

Dennis

Here's how mine sits…

Dennis