I am looking at buying a F33A which is turbonormalised. Does anyone have
any knowledge about the value this adds to the aircraft. I know the cost
of
fitting but this one was done in 1991, and it is the original turbo. How
much does it add to the value of the basic aircraft?

This is all from memory so I hope the facts are correct. Remember what you
paid for this advice.

The TN system was probably done by the outfit in Pagosa Springs. I forget
their name. Some folks have had good luck with these, but I had a friend
who had a complete engine failure due to to cracked oil housing - they later
determined that the housing cracked because someone used it as a pry-point
while putting in the turbo and others have reported general sloppiness in
how they did their installations. The STC was sold to Tornado Alley
(www.taturbo.com) which has it now and I think provides good support. These
guys are highly regarded. I'd contact them about this airplane and see what
they know about it - they may have seen it before or have further records.

I'd feel more comfortable about a TN Bonanza if it has the VERY best cooling
mods and the VERY best engine insturmentation including six-point EGT and
CHT. TN works, but it really puts the onus on operating the engine within
limits on the pilot - you no longer have the safety net of the engine making
less power as cooling drops off with altitude. Many think the 550 holds up
better than the 520 with TN.

Of course, you want the best pre-buy money can buy.

As to value, I'd guess about 50% of the cost of doing the Tornado Alley
installation from scratch or about $25K. I think they've made some big
improvements in the last 13 years, and turbos wear out, so I don't see it
commanding more than this. If the seller wanted $40K extra for the TN, I'd
rather buy a normally aspirated plane and spend the extra $10K and get a
fresh installation with the latest/greatest stuff.

I assume you've made sure you really need the turbo. Personal prejudice
here, but the 520/550 has never been an engine that takes to turbocharging
as well as the Lycoming 540, perhaps because it doesn't use sodium valves
like the Lyc. And anytime you add a turbo, you raise the spectre of any
fuel leak leading to an engine fire, something that almost never happens
with normally aspirated engines - there have been some grisly engine fire
accidents in turbo Bonanzas. So if it were my money, I'd take the extra
dough for the turbo and buy an A36 as I'd use the room, useful load, and
larger CG envelope a lot more than I'd use the turbo. I'd also enjoy the
much nicer panel of the A36. Or I'd ante up to the A36TC or B36TC. A turbo
on an F33A results in a plane with great trip capability for light loads,
but most folks who take trips want to carry more people and stuff. But this
is all personal tradeoffs.

Good luck,

- Mark