did Germans use downthrust?

[Douwe]

Hello,

From everything I can determine, it appears that the Germans didn't use downthrust.

Does anyone know if this is why all pilot reports mention that they are tailheavy with power and nose heavy in glide? I am not an expert, hence my question, but wouldn't a lack of downthrust cause these very symptoms?

It sounds like it might be wise to add two or three degrees. nobody would ever know and it might fly nicer.

??
Douwe

[jumpinjan]

Douwe,
That's a very good question.
Have you read the McCook Field's performance test of the Roland D.VIb? The pilot indicated that the plane's balance is normal, "The balance is normal, tail heavy with full engine and slightly nose heavy at slow speed with engine throttled. In a glide it will balance without the use of the controls. The lateral balance is good..."

[vongrube]

Douwe,
This condition is created anytime you have a high lift wing condition. Under full power and / or high speed conditions the nose will pitch up, requiring the pilot to add down elevator. In the Fokker triplane, there is also an added problem with the top wing being so far from the center of thrust line.
Most airplanes have a pilot activated pitch control to compensate for this problem. However most WW1 aircraft did not have this feature, and washers or spacers were used under the horizontal stabilizer to add a few degrees incidence. Usually from 2 - 5 degrees incidence was the standard.
Also, the location of the horizontal stabiler in relation to the center of thrust line can have either positive or negative effect on the pitch problem, which is why you see some aircraft with a T-tail design. The Piper Tomahawk was horribly nose heavy in all conditions..even while in taxi mode!
I never liked that aircraft!

[mustang]

Vongrube

I disagree with you about the Tomahawk. If you decease the power the nose sinks, if you increase the power the nose rises. That is the way the aircraft is designed. I operated five of these aircraft in a flight school over a period of 10 years for between 35,000 - 40,000 hours, includiing about 3,500 personal hours.

We did our own maintenance and if the trim system is rigged correctly the aircraft was able to be trimmed out throughout the normal speed range. In my judgement it was a far better elementary trainer than the insipid and bland Cessna series.

I base my assessment on 10.000 hours of military and civilian instruction.

Regards

Mustang

[vongrube]

Dear Sir,
Did not the Tomahawk have a deserved reputation for PIO?
I have read many accounts (complaints) about this condition, seen it with many new pilots, and experienced it myself. It was very touchy in pitch mode..not necessarily an admirable trait for a training aircraft. But thats just my opinion. I hated its heaviness while in taxi mode, and it just felt odd to me, and twitchy close to the grouind. While I loved the visibility, and low wing configuration I hated the machine as a whole. I saw more Tomahawks than Cessna 150s with their nose wheels torn off.
Again..to each his own.
Curious...you just don't see many of them here in the states anymore. Wonder why?
Regards
Vongrube

[vongrube]

Correction Mustang..
Did not the Tomahawk have a reputation for aggravating PIO?

I have to agree with Mustang. Did nearly all my training in a T-Hawk back when I was 15 yrs old (nearly 30 yrs ago now) and found it to be a fine trainer. My instructor was a 27K hr WWII vet that flew C47s over the Hump. We did everything including spins. The plane developed a bad rap that I can only attribute to pilot and trainer competence issues.
I've flown a lot of types since then including several hundred hrs in taildraggers and I'd still fly a T-hawk any day. It's an honest airplane.

Just MHO...

[Douwe]

I know that increased power/speed will increase drag on the wings and if they will tend to swing the fuselage up around the upper wings, this is fairly normal. It seems however, that it was so pronounced with WWI planes that this longitudinal balance shift was considered "normal".

I am wondering if one wouldn't be wise to add a few degrees downthrust to reduce the tendency a bit.

I am building an albatross, so can't shim the horizontal stabilizer, which leaves the control stick lock to handle unbalanced trim characteristics.

It certainly won't do any harm and, it would gentle the stall character somewhat, too. Anyone building a WW1 bipe today has to contend with alot of different issues than the fighter pilots of 1917 did.

Generally, you have err on the side of caution and, you're not trying to push the airframe for absolute max performance. So a few little tweaks here and there to make it fly easier aren't really a crime, in my view.

What do I know, I'm just an RC pilot.

F=MA

You could add *gasp* a trim tab to the alby's ele....

[Machinbird]

Douwe, You could also add an adjustable spring mechanism to the elevator cable system of the albatross. Had an old Luscombe once which used that method quite effectively. That way, you wouldn't be making external changes.