Beagle Pup experiment

Everything in connection with developing aircraft for FlightGear
sanhozay
Posts: 167
Joined: Fri Sep 25, 2015 5:59 pm

Re: Beagle Pup experiment

Postby sanhozay » Mon Nov 14, 2016 11:05 pm

I'm using full throttle, yes. Brakes off, then smoothly increase throttle. Putting two and two together from your post on engines, I suspect you are going to tell me that I should be setting a takeoff thrust using RPM?

User avatar
IAHM-COL
Posts: 6455
Joined: Sat Sep 12, 2015 3:43 pm
Location: Homey, NV (KXTA) - U.S.A
Contact:

Re: Beagle Pup experiment

Postby IAHM-COL » Mon Nov 14, 2016 11:30 pm

can I get the takeoff RPM too :D
I push that thing till goes round, then I go run/
https://raw.githubusercontent.com/IAHM-COL/gpg-pubkey/master/pubkey.asc

R.M.S.
If we gave everybody in the World free software today, but we failed to teach them about the four freedoms, five years from now, would they still have it?

bomber
Posts: 1379
Joined: Mon Nov 30, 2015 3:40 pm

Re: Beagle Pup experiment

Postby bomber » Tue Nov 15, 2016 11:26 am

Just wanting to know if you were smoothly increasing the throttle that's all.

with regards steering... your rudder is linked to the steering, yes ?
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchell

sanhozay
Posts: 167
Joined: Fri Sep 25, 2015 5:59 pm

Re: Beagle Pup experiment

Postby sanhozay » Tue Nov 15, 2016 12:34 pm

Yes, smoothly.

For me, the rudder control is definitely steering the nose wheel in your FDM, it's just that it's only moving it a tiny amount.

I have acquired a Beagle Pup 100 checklist. I can't reproduce it here but a couple of figures to keep in mind are the quoted climb speed of just 65kt and normal cruise of 85kt at 2300rpm.

bomber
Posts: 1379
Joined: Mon Nov 30, 2015 3:40 pm

Re: Beagle Pup experiment

Postby bomber » Tue Nov 15, 2016 12:59 pm

Sanhozay, would you consider a review of the engines and prop from our fdm's, we could maybe also work on the DRI's engine/prop combination as a proof of method.

I'll have a look at my keyboard.xml file and see if sometime in the past I modified it to link the brakes to the rudder.... clutching at straws here.
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchell

Richard
Posts: 114
Joined: Sun Sep 11, 2016 5:57 pm

Re: Beagle Pup experiment

Postby Richard » Tue Nov 15, 2016 10:12 pm

For all surfaces I've double checked and fixed the geometry (positions), the airfoils (the wing root was not identical to the tip), the dihedral and incidence of the wing, and the centre of gravity and mass/balance including tuning of the moments of inertia. I've tuned and adjusted Cl, Cd and AOA to get closer to Nick Lawson's AIAA paper - but I'm still a way off matching the figures (and I'm not sure why that is). In the interim I've added a fixed amount of 0.012319 to Cd to account for the missing drag - but this is a very blunt method and needs refining.

Uploaded a new release to my site: http://chateau-logic.com/sites/default/ ... 6-11-15.7z

From my flight testing (of my own model, which is never reliable) it seems still to be too performant even with the revised drag, but more worryingly I can get into quite a strange situation with an excessive amount of sideslip in turns and/or high pitch. I think my aero is still a bit twitchy in the pitch control - but at the moment I'm at a loss as to why.

sanhozay
Posts: 167
Joined: Fri Sep 25, 2015 5:59 pm

Re: Beagle Pup experiment

Postby sanhozay » Tue Nov 15, 2016 11:25 pm

bomber wrote:Sanhozay, would you consider a review of the engines and prop from our fdm's, we could maybe also work on the DRI's engine/prop combination as a proof of method.

This sounds like a plan. The prop and engine are critical to all three FDMs.

I regenerated my prop and aerodynamics configuration with Aeromatic++ and everything is now well beyond the painful 500fpm climb out at 65kts that I believe to be correct. I'm going to be busy now until Friday but I'll get back to it then.

What's DRI?

Richard
Posts: 114
Joined: Sun Sep 11, 2016 5:57 pm

Re: Beagle Pup experiment

Postby Richard » Wed Nov 16, 2016 12:58 am

After some feedback from Vincent I've put together a revised FDM with only 33% of the pitch moment due to elevator.

This needs testing. It certainly seems a lot less twitchy to me. This file is here http://chateau-logic.com/sites/default/ ... up-vsp.xml - just drop it in.

Of course if the general opinion is that this is better then I'll need to figure it out; rather than just taking 1/3rd of pitch moment as that's not a general solution.

User avatar
IAHM-COL
Posts: 6455
Joined: Sat Sep 12, 2015 3:43 pm
Location: Homey, NV (KXTA) - U.S.A
Contact:

Re: Beagle Pup experiment

Postby IAHM-COL » Wed Nov 16, 2016 3:57 am

IAHM-COL wrote:@bomber

My video

Flying the T4T-beagle
AVAILABLE NOW

Notes:

***
https://raw.githubusercontent.com/IAHM-COL/gpg-pubkey/master/pubkey.asc

R.M.S.
If we gave everybody in the World free software today, but we failed to teach them about the four freedoms, five years from now, would they still have it?

KL-666
Posts: 1610
Joined: Mon Sep 28, 2015 8:42 am

Re: Beagle Pup experiment

Postby KL-666 » Wed Nov 16, 2016 11:04 am

Hi Richard,

Wlbragg describes exactly my experience in all it's detail.

Maybe a little better. It doesn't seem to be too much authority, it is more like too little authority on the opposite side. When you make a pitch change it wants to continue in the direction of the pitch and you need to over compensate to get control again. That leads to a vicious cycle that I pretty much always end up loosing. I cant make an approach and flaps seem magnify it.


It is like a huge weight is set in motion rotating around the lateral axis. Setting it initially in motion is easy, but after that, the rotating weight is hard to stop, and over correction happens easy. At low speed it is at it's worst, with or without flaps. I can't tell if flaps make it even more worse.

My greatest suspect is that there is some huge effect calculated from a change in AoA (wing or hstab), which is hard to counter. Second i would experiment with the CG. Maybe it is too close to CL or too far forward. Too far forward can have adverse effects too, specifically in the area of sluggishness.

Kind regards, Vincent


Return to “Aircraft Development”

Who is online

Users browsing this forum: No registered users and 17 guests