Miller conversion questions

[Andrew Fay]

In my search for a 260B I strayed into the twins. I found a miller conversion an was impressed with the idea. I went to look at the airplane and took pics of the logs so i could study in detail when i got home.

Upon looking at the currnet W&B I found something that discouraged me. It looks like after all the converting there is not associated increased Gross Weight. That means that this particular aircraft has only 1000LBS usable. You would think the wing lockers and the big engines would give you room on the zero fuel weight and engines and nose baggage would prompt a GW increase.

Am I right in my study? Is the miller that limited on GW?

Thanks

[Zach Grant L1011jock]

In a word, yes. The maximum LEGAL gross weight of any twin Comanche is 3800#, and that is only available through the addition of a Robertson High Lift kit. Tip tanks get you 125 extra pounds of fuel, and miller integral tanks also get you an additional bit of weight ( can't remember the exact number but 75 sticks in my mind for some reason), but the extra stuff hung on the aircraft for the Miller mods did not raise the gross weight.

[Andrew Fay]

Well, thats a real let down. Im sure lots of people just fly overwieght but I cant really hang my ticket out there like that. Gots to do it by the letter of the law.

[Kristin Winter]

It is possible to find twins with 1200+ lbs of useful load. My "C" model is just shy of 1200, but I have deicing which adds significantly. I do have the tip tanks that add 125lbs of useful, less the weight of the installation. Considering that the twins don't burn that much more than the singles, that works out to be about 500 miles of flying with 800 lbs in the cabin. I have also taken my 120 gallons of fuel and flown 1200 nm with just myself on board.

[Zach Grant L1011jock]

I had a 63 Normally Aspirated twin with a true 1400# useful load (I weighed it). It had tip tanks, and was overall a clean light aircraft with no mods to add weight. It also trued out at almost 170 kts stock, no speed mods. It was strait, with no damage history. They are out there!
-Zach

[Andrew Fay]

Thanks for the info guys, Im still leaning towards a single for a few reasons but we will see what comes out of the woodwork.

[Jay]

I have 1,198 useful in my twin. That's with the Robertson GW gain, but also includes some heavy stuff like turbos, a leather interior, nice carpet, etc. An early NA Twinkie with a fairly stock interior and no speed mods or de-ice gear but new radios would probably be the useful load champ.

Jay

[N3322G]

Before all the mods and total of 10 fuel tanks, the 1970 PA39 had 1342 useful load. Now we are at 1151.54 approximately

By the way, it might or might not be worthwhile checking the math. On the 2010 annual we found 3 separate CG calc errors as well as useful load errors. We documented it and now have correct data int he Flight Manual.

[MULEFLY]

N8982Y 39-147 has a 1254 pound useful load... Robertson Mods give it a net of about an additional 175#... I have the automatic flap retraction kit that adds a few pounds. The 3,800 # Max Gross Take Off Weight -- no tip tanks...

Jim

[Don Nelson]

Hello Andrew,
A legal 1000# useful sounds about right, unfortuneately.

My Miller Turbo 30B, serial #1266, with Robertson Hi Lift, Arapaho WS, Tip Tanks, Wing Lockers, Radar, but no nose locker, reportedly weighed 2835# when I purchased it last summer.

Since then, with an extensive panel upgrade, (that incidently dumped the radar), it was weighed at 2813# including 6 gal's unusable fuel. Leaving N12FS with 987# useful.

Goes pretty good tho. (-:

Don