Conspicuous by Their Absence

[womble55]

Hi everyone, I'm inches away from finishing my Wellesley (a couple of bleeds, wing roots to build, a couple of missing panels and the U/C parts to arrange) but I cant get the Air file right. 1) The aircraft flies hands off but gradually banks left. 2) I've altered the engine specs in the Air file to read correct for a Bristol Pegasus i.e.(9 cylinders + displacement per cylinder + max RPM + max HP) but when on a test flight the indicated HP using the test gauge says 1459 HP and rises to 1600HP with supercharging. The gradual bank has got me scratching my head but the engine misreporting is annoying me totally. Do I put incorrect info into the Air file so my reported HP is correct or do I keep the correct info.

[Ivan]

Hello Womble55,

A Wellesley would be a cool addition to the CFS menagerie. Please send me a zip of the the aircraft so I can check it out because otherwise I would be just guessing. If you haven't already, you can check out the "Engine Tuning Tutorial" I have been working on because it would probably address a bunch of issues you are probably running into.

And Post some screenshots! A Wellesley is an interesting looking bird.

- Ivan.

[womble55]

Hi everyone, I'm afraid you will have to wait for the Wellesley pics as I am currently on vacation, a week in Lyme Regis. With my job, I usually get up at 04:30 so what happens when I go on holiday? Its 05:30 now so Here is my take on the problems.

I think the gradual left bank is due to insufficient dihedral, also the ailerons and elevators are way too sensitive so are probably contributing to the instability. So that will be my first port of call.

The Vickers Wellesley has been in my Projects folder for an awful long time, it took me a couple of years to get a decent 3-view. Unless you know the history of the Wellesley then you are up the creek without a paddle because the majority of 3-views were either of the prototype or the examples from the LRDU. Easy to know which is the prototype because the tailwheel was encased in a spat and the LRDU had long chord engine cowlings. Incidently the Mk2 wasn't a Mk2 at all but a heavily modified Mk1 with added inter-cockpit glasswork.

The model has had several fuselages, wings, cockpits and engines but the current example is up to scratch.

Dawn is now breaking and the view is stunning, no chickens to put out..........time for another cup of tea.

see you all next week

[Ivan]

If you are still having issues with the Wellesley, I can check out the AIR file if you email it. It would help to see how it lines up with the visual, but that isn't absolutely necessary.

- Ivan.

[womble55]

I'll have a go first, drop the sensitivity a tad, after all the pilot of a Wellesley wasn't expected to pull large amounts of G as in a P51. Once the list and the snake from the oversensitive controls is sorted I will send you a pre-publication version of the Wellesley.

The model is currently in it's fourth or fifth version, this was partly dictated by the fact that it was two years before I acquired a decent three view of a Mk1 Wellesley. Incidently, there wasn't a Mk2, just a version used for test flying adapted with a continuous canopy between the cockpits. The three views available when I started the project were either of the prototype or a Mk1 of the LRDU. Both are easily identifiable, the prototype had a spat on its tailwheel and the LRDU Wellesleys of the LRDU had long chord cowlings over their Bristol Pegasus.

see you all after my vacation

[Ivan]

Hello Womble55,

Take your time. Enjoy your holiday. Send me a copy if you believe I can help. I also have a similar list on my Lavochkin fighters. I never went back to fix it. Perhaps setting a bit of trim before take-off is sufficient?

- Ivan.

[womble55]

Hi Ivan,
I tried setting the trim but because of the over sensitivity it then lists to starboard, in fact this is what put me on the route to decrease the sensitivity and the apparent lack of dihedral.

Its now the last day of my break and I'll be on my way home tomorrow so with a bit of skill I will be back on my PC but the garden has been left to its own devices for a week and the triffids will need shooting.

[Ivan]

Hi Womble55,

Are you setting the trim effect per notch in the AIR file or setting a notch or two of trim as you fly?
I don't believe there are any static trim settings (initial trim) in the AIR file.
If you found some parameters that work this way, please let me know where.

If it is one notch of trim that makes it lean the other direction, you need to lower the effect of the lateral trim.
I find that the stock aircraft all have way too coarse trim to the point that although you can trim to compensate for battle damage, you basically can't trim the aircraft to fly hands off. Trim settings for my aeroplanes tend to be just a fraction of the numbers for the stock aircraft.

- Ivan.

[Ivan]

....A couple more thoughts if you are starting with the P51D AIR file.

Set the stuff you basically know in the AIR file before you really get to tuning:

1. Wing dimensions
2. Zero Fuel Weight
3. Guess at the inertias. I would guess that all of them would be way higher than the P51D, especially roll and yaw.
4. Increase the damping effect on every axis, especially roll. That HUGE wing is going to make rolling VERY slow.
5. This critter carried HUGE fuel tanks. Add those and see if your aircraft becomes much less sensitive.
6. Get the basic armament weights correct. 2 x .303 I believe.
7. Get the basic engine performance and adjust drag.
8. Landng Gear and Cockpit Viewpoints.

Before you do the basics, tuning is a waste of time because some of the factors I mentioned are going to change the handling substantially.

- Ivan.

[womble55]

Hi Ivan,
Thanks for the pointers, I did start with the P51 Air file and I have a direction to take now. I haven't managed to find the fuel loading online yet or the ammunition loadout. A lot of answers are false as they refer to the LRDU Wellesleys which had most military equipment removed for their flight to Australia. They also had extra tankage for the trip but I do have a 'Flight' magazine cutaway which details the tank positions but it is in French and is taking a while to translate. You develop many skills in this game don't you!

[Ivan]

Hello Womble55,
We all develop more skills and understanding of how things work in the flight sims if we are willing to mess around a bit and see what the result is. I have no idea what the proper fuel capacity information is for the Wellesley Mk.I or which ever Mark it is that you are modelling. Searching the Internet hasn't produced anything for me yet. It just occurred to me that I might have one more source which I will check before I go to bed.

I was looking back over the start of the discussion about the Wellesley and it engine power output. If the Engine Tuning Tutorial didn't help, I believe the issue is that the manifold pressure of the Pegasus engine is much much lower than that of the Merlin in the P-51D. I will see if I can come up with any numbers there as well.

As for ammunition load for the Wellesley, I am guessing that it carried a LOT of ammunition for the two .303 machineguns that were mounted. This is the kind of aeroplane the British tended to use in remote areas without good supplies.
I have .303 British Ammunition as weighing 1.05 ounces per round and link.

Hope this helps. I will post additional data if I can find it.
- Ivan.

[womble55]

With all of the trawling of the internet, all I can find for the Wellesley is 3000 rounds of ammunition but this is on one site only.
The fuel load, I think, is around 450 gallons (this was done by reverse mathematics from info gleaned from one site that said the fuel load for the LRDU was increased by x amount) but the quantity distribution still eludes me.
On the plus side, I have increased the wing tankage to an initial 220 gallons and reduced the aileron sensitivity and she flies much better.
Thanks for the pointer regarding the specifics of the Bristol Pegasus, hopefully I can get the engine tuned correctly.
On the down side, I'm back from holiday and I am now getting ready for work.

[Ivan]

Hello Womble55,

I don't believe you understood what I was getting at. The Aileron Control Effect is one thing, but the Roll Damping (Record 1001?) is what I believe should be changed. Even if the Ailerons were just as powerful, double the wingspan and about three times the area is going to slow things down a bit.

Here is what I could find about the Bristol Pegasus XX:
Bore: 5.75 inch
Stroke: 7.50 inch
Diameter: 55.3 inch (For the visual model)

0.5 : 1 Reduction Ratio.
87 octane fuel.

Ratings (From Janes):
925 HP @ 2475 RPM for Take-Off (but note that Max RPM is 2600 so why is Take-Off Limit so low?)
815 HP @ 2475 RPM Climb Power (@ 4500 feet altitude)
575 HP @ 2200 RPM Cruise Power (@ 9250 feet altitude)

Janes says 860 HP @ 2600 RPM for all out power, but I believe this is a typo.
I believe 960 HP is what was intended.
See the attached graph for manifold pressure settings (+4.25 pounds) and rated altitude (8500 feet).
I have a conversion spreadsheet for pounds boost to inches Mercury in the Engine Performance Tuning Tutorial.
I believe the graph agrees more with 960 HP as all out power.

From the graph, I believe there is sufficient information to generate a pretty good CFS engine.
The original graph was too high resolution to upload so I had to reduce and rotate.
Funny thing is that this upload is about 100K heavier than the original.
Let me know if you want the original which isn't any more readable than this one.

Hope this helps.
- Ivan.

[womble55]

Hi Ivan,
I had all of the Bristol Pegasus specs from Wikipedia, they said more or less the same. Wikipedia is a great source for all aero engines including the more obscure like the Armstrong Deerhound and Boarhound.
What I have found though is the ammunition load out for the Wellesley, not on the Internet but with good old paper and ink. I managed to get hold of 'Warpaint No 86' from eBay and its an absolute gem.
The front gun (Browning) had 97 rounds whereas the rear gun (Vickers) had a total of 600 rounds. I believe the information to be correct and just plainly disbelieve what was found on the internet.
The flying has improved greatly by decreasing the values in 1001, to such an extent that long distance flights are a pleasure to do.
I still have some bleed issues, some missing panels have been sorted plus a couple of small items still to build.
I can see the light at the end of the tunnel.

[Ivan]

Hello Womble55,

I am pleasantly surprised that Wikipedia has that much information on the Bristol Pegasus.
The only thing I found that they didn't list was the Manifold Pressures.
Did you ever find the Propeller Pitch Range? I never found that OR the Propeler Diameter.

Regarding the ammunition loadouts: I am a bit skeptical about 97 rounds on the fixed Browning MG.
Considering that the Browning fired at around 1200 rounds per minute cyclic rate, 97 rounds gives not quite 5 seconds of fire. I was guessing around 2000 rounds but your 3000 rounds sounded quite reasonable.

- Ivan.

[womble55]

Hi Ivan,
I was surprised at 97 rounds too but further into the book it states that the forward firing browning ammunition box contained 650 rounds. It also states that the propeller was a De Havilland ( Hamilton Standard) two position prop of 12ft 6ins diameter. As for the pitch angles, that one eludes me.......for now.

Ps. After a swift search I have found that Hamilton Standards had a pitch range of 15 degrees to 45 degrees, this is for the constant speed units and not the two pitch type so further research is required.

[Ivan]

I don't believe all Hamilton Standard Propellers had the same pitch ranges. Note that the propellers on the Japanese A6M Type Zero Fighter only had a range of about 20 degrees and for the A6M5 was 29-49 degrees. This is a pretty reliable number since it is from their own operations manual for the type.

It is also possible to have the pitch range out of adjustment as was done with the A6M2 captured by the AVG and tested.
This implies that the low and high pitch stops were changeable and might vary significantly between types.

- Ivan.

[womble55]

Hi everyone, as promised here is an early version of my Vickers Wellesley. There is still a lot to do, bleeds, minor construction alterations and the usual tweeks to get things right. The Air file isn't quite right but I am working on it as we speak.
This is one of the aircraft that I believe to be missing from our hangers for way too long, the aircraft from the late twenties and early thirties are sadly lacking. A shame really because the majority of aircraft that we do have in our hangers wouldn't be there if it wasn't for the missing examples.

[Ivan]

Hello Womble55,

Cool Aeroplane! This thing is HUGE!

I poked around at it a couple hours ago and found a few issues that don't look difficult to fix.
Should I email you? Don't know if I still have your email address.

- Ivan.

[Ivan]

Hello Womble55,

Is this one also yours? I believe this project has been on my computer since about 2006.

- Ivan.

[womble55]

Hello Womble55,

Is this one also yours? I believe this project has been on my computer since about 2006.

- Ivan.

Yes, the project has been going for an embarrassing long time and has had new engine, wings, cockpits, fuselage. In fact it has been rebuilt more times as and when my skills improved. Most of this was due to the lack of a decent drawing of the correct Mk1 and not of the prototype or one from the LRDU or the Bristol Hercules test bed.

[Ivan]

Hello Womble55,

Decided to reply via PM rather than email.

- Ivan.

[womble55]

Hi everyone, must thank Ivan for the Air file pointers, the Wellesley flies like a dream. I have rebuilt the rear fuselage, added blanking for the cockpits and at the moment trying to sort out the U/C bleeds. Hopefully it will be uploaded in the near future.

[Ivan]

Hello Womble55,

I actually spent a fair amount of time poking at the Wellesley AIR file because I thought it would be a good test of whether I could easily accomplish again what I described in the Engine Tuning Tutorial. It was fairly easy.

The other thing I noticed about the Wellesley was that it had a large wingspan with very minimal dihedral. I believe an aircraft like that tends to have a flat yaw from rudder input alone and because the original came from the stock P51D, it needed a fair amount of tuning.
I was trying to see if my process for tuning the B-25C Mitchell was reproducible. With a bit of effort, I found that a lot of my notes were not quite thorough enough and some were outright wrong. I got more or less the effect I was looking for with the Wellesley.

Tonight, I went back to see if my additional notes from the Wellesley would make fine tuning the B-25 easy. Turns out that they do not. Just about every change I made had some kind of unintended side effect. Yet more refining is necessary and I am back pretty much to where I started with the MitchellC's AIR file....

I just hate it whennat happens!
- Ivan.

[Ivan]

This is a bit off topic, but here goes:

The last few days have been a bit rough around our household.
My 11 year old son had very bad stomach pains and had to go to the Emergency Room.
Turns out he had appendicitis and had to have surgery to remove his appendix.
It is hard knowing someone is about to cut open your little baby even if he needs the surgery.

We got back from the hospital yesterday and although he is still in some serious pain, he seems to be getting better. He can barely walk right now so he will be out of school for a couple days more.

He still doesn't eat much but that appears to be improving as well.

- Ivan.