Tipsy Nipper C of G

[Sharps1864]

Hello,
I have a question concerning the C of G of the Tipsy Nipper. The LAA limitations doc quotes 14.3" to 16.5" whilst the owners handbook quotes 15.0" to 18.5". Can anyone shed any light on this difference please ?

[Chris Martyr]

Hello Joseph,
Can't unfortunately give any concrete facts on this one, and also noticed that LAA have no data sheets [TADS] for the Nipper.
The discrepancy could depend on a couple of factors though:

Is it a VW engined Nipper? as some where re-engined with Jabiru's I believe.
Is it cleared for aerobatics, as I believe that there could be a normal and a utility range for its CofG limits .

[Ian Melville]

Is the same datum point used?

[Sharps1864]

Thanks to all that have responded to this question. The confusion has been cleared up by the LAA, the rule is "stick to the LAA limitations" it makes sense.

[MikeM]

A friend who has a couple of Nippers, including one nearing completion after a 10 year rebuild, related the following:

"Nipper MkII had Stamo 1400 engine as standard weighing 121lbs and CG limits 15-18.5 ins aft of of L/E. AUW was 660 lbs.

MKIII Nipper was fitted Rollason Ardem weighing 158lbs requiring addition of approx 9 lbs of lead ballast mounted permanently in the tail, all of which added to increase in the AUW from 660 lbs to 725 lbs. Up to and including this weight, the CG limits must always lie between 14.3 -16.5 ins aft of L/E. The load factor also decreased from 6-3 to 4.4-1.75 unless flown at 660lbs i.e. fuel restricted to 3 gals and no luggage with pilots restricted to 116 lbs - 168 lbs. Wing L/E remains datum for CG both marks."

[JimCrawford]

Mike, I can't understand how you put those numbers together.

The utility max weight of the Mk11 was always 725 lbs and the aerobatic weight 660 lbs. It was never increased from 660 to 725 to take account of a heavier engine. I find the difference in weight you state between the Stamo and Ardem engines of 37lbs a bit high, that is a quarter of the weight of the engine, but I imagine the 'Peacock' style mags and chain drive of the Ardem would account for a large part of that. My Nipper, a Mk111 (Ardem), has an empty weight of 457 lbs against a Mk11 (Stamo) handbook weight of 448 lbs and I would guess that the difference is due to the engine change. Again, in my Mk111 there is no 9 lb ballast block down the back and no evidence of there ever being one. The Mk111 drawings I've seen do not show tail ballast, or any provision for it. The most forward CofG position I have is 14.9" aft of datum so quite forward, probably due to the heavier engine, but well within the LAA limitations (14.3" - 16.5") and very nearly within the original manufacturers numbers (15" - 18.5"). I have no idea as to why the CofG range was changed, or who did it. It would be interesting to know.

I scanned through GINFO to see if I could find any rhyme or reason for the Nipper weights but the MTOWs of the UK fleet seem to be all over the place with 660, 725, 748 (most common) and even one at 770 lbs. My LAA document states 684 lbs aerobatic , 748 utility. which I believe to be an LAA dispensation as I have a CAA authorisation for the aircraft at 725 lbs. dated 2nd June 1978.

The load factors in the posting are plain wrong. The Mk11 and Mk111 aircraft were rated at +5 -2 by the manufacturers, never +6 -3, and the revised figures, on my 1978 CAA release and my LAA permit limitations, are +4, -2. The +6 -3 and +4.4 -1.75 numbers are a misapplication of the terms 'aerobatic' semi-aerobatic' and 'utility'.

The LAA operating limitations were generated a long time ago and I think you would be kicking a dead horse trying to find out the rational behind it all. nobody at the LAA has the time to trawl the records, which may be incomplete anyway.

Jim
(GAVTC)

[MikeM]

Jim, as I stated, their not my numbers but from a friend. He's experienced in Nipper restorations and worked for Nipper Aircraft in the past. If you pm me with your phone number I'll pass it on so you can chat to him directly.