Had a really fun day completing the flying portion of my High Altitude Endorsement for my Superstar 700 Aerostar as I am increasing the cabin differential to 5.5 from 4.25 (provides an 8,000' cabin at 25,000' and a 10,000' cabin @ 28,000) which increases the certified ceiling to 28,000'...thus the reason to get the endorsement after flying Barons for 2,000+ hours including about 850 hours in the P58 Baron.

What a simple procedure on this Ted Smith designed aircraft:

*Don O2 mask and ensure 02 is flowing
*Close throttles (will depressurize cabin as throttles are reduced past 20")
*Pitch of 215 KIAS and declare emergency

From 23,000' the descent rate was an impressive 6,500 pfm in that thin air! The plane handled and felt the same as flying at 140 KIAS. Performed the emergency dive wearing foggles to simulate IFR conditions (actually it seemed easier to do "IMC" than visual, but visual does provide an amazing view of the earth filling the windscreen).

Rolling the plane into a 30 degree bank while descending produced a similar descent rate (and was really fun to do). Amazing to watch the the altimeter unwind at such a fast pace and to watch the Aspen PFD display its warning "chevrons" (big arrows indicating to pull up). Rounding out the dive while adding power was easily accomplished. The depressurization of the cabin from pulling the throttles closed was a non-event as the cabin slowing depressurized...you felt it in your ears but nothing dramatic and easy to clear your ears (certainly an explosive depressurization caused by losing a window would be harder on your ears, but recently talked with a pilot who experienced losing a rear cabin window and he said while there was a lot of wind noise, it wasn't that bad on the ears). Descending @ KIAS of 148 with gear down and full flaps and power reduced to just 20" to hold cabin pressure produced a 3,200 fpm descent and a 3,800 fpm descent with the throttle closed and of course the cabin pressure loss.

What a fun, fun day of training!

Tom

5.5 diff is great, didn't know they could go that high. Better than a C90GT!

Tom what a great experience!

Now my curiosity has me asking what kind of fuel efficiency can you get up at 25000?

Hi Matt...of course it depends on the power setting...in "go far" mode, you pull power back to 25" and 2,000 rpm @ about 23.6 gph (about 42%+ power) for about 208-210 KTAS...or you can go fast @ 65% power @ 44 gph (32"/2,200) and get 250 KTAS...or 75% power (35"/2,200) 48 gph and 260 KTAS. Suspect the new 28,000' ceiling will provide a few more knots.

FYI...at 10-12,000', "go far mode" of 23.6 gph produces 178-182 KTAS.

Very "late model King Air" like speeds but of course without the Pratt reliability, beta a big cabin. Can climb at full power (84 gph @ 42"/2,500 rpm @ 128 KIAS) and get 2,300 fpm+ or climb @ 72 gph @ 26"/2,400 rpm @ 155 KIAS for about 1,500 fpm or @ 170 KIAS for 1,000 fpm or do economy climb like I did in my old B58 Baron @ 35"/2,000 @ 48 gph and 1,000 fpm @ 140 KIAS.

See the Feb. AOPA magazine for a look at the Aerostar "jet"...as the plane was designed to be a jet back in the 70s but no suitable engine available...so it has an incredibly strong airframe with a never exceed speed of 244 KIAS (but the uncertified jet shows a VMO of 280 KIAS).

Tom

Tom,

Did you also do the emergency turbulence decent really dirty? That is even more fun and gives you a really interesting view of the ground.

-- Props full forward
-- Engines to idle
-- Speed brakes out
-- gear out
-- full flaps

Pitch for KIAS 140. From what I recall, it was roughly a 35 degree down angle and 8000FPM descent. I have not done it in a while, but man is it fun to do both the high speed and turbulence descents.

Tim

Hi Tim...yes did the "dirty" turbulence emergency descent as well @ 148 KIAS (speed for full flaps/45 degrees, gear and props forward but only got 3,800 fpm per minute but that was from 17,500 where the air is thicker than the "clean" dive I did from FL230 where I achieved 6,500 fpm @ 215 KIAS)...but I do not have speed brakes. WOW Tim...with your speed brakes you got 8,000 fpm!!!!...and I though 6,500 fpm was impressive...I am a slacker!

Pretty darn COOL airframe Ted Smith designed.

Best,

Tom

Tom,

I never did look into why, but when descending from 25K versus 15K you get a much higher descent rate for the KIAS. Maybe someone on BT can explain it

The speed brakes are good for another 500-750FPM when low and 1000-1500 when high.

Note: I have the Precise Flight under wing scissor brakes.

Tim

Wow! That's impressive speed on such a low fuel flow.

I just made a flight at 11k in my baron burning 23.5 and getting 180kts. Your doing the same fuel flow and 30 kts faster! Plus I've only got about 10 more kts available more gas. You've got all kinds of more speed available if you want to burn the gas.

Cool airplane!

I have considered that mod to get the increased 5.5 pressurization. Who is doing the mod on your airplane? What is involved? What did it cost?

I rarely fly above 20k anyway but regardless it would make the airplane more comfortable at all altitudes.

The 601P's will get even better fuel economy due to their high compression engines. You do sacrifice top speed and longer takeoff as they have less hp, though.

The Aerostar is probably a bit slipperier than a Baron but turbos and high altitude are the key to going fast on less fuel. I wonder what the FF is in the Aerostar for 185 KTAS at 9000 MSL.

I had it done by Aerostar Aircraft. Check the website for the current price, or just call Jim Christy.

Tim

From a trip to Nashville a couple a months ago:
MP: 24in
RPM: 2040
FF: 14.8-15.2 per engine
TIT: 1590-1620
Altitude: 6500
KIAS: ~170
KTAS: ~190

I have a few trips later in January. Do you want the performance at 9K MSL or when the cabin has a 9K MSL?

Tim

The Aerostar is probably a bit slipperier than a Baron but turbos and high altitude are the key to going fast on less fuel. I wonder what the FF is in the Aerostar for 185 KTAS at 9000 MSL.

I am thinking it's because your TAS is higher the higher you go, for the same IAS, and much of that speed vector is pointed downward during the emergency descent. Right? Wrong?

I hope you guys are precooling the turbos and the cylinders carefully before "fully closing" the throttles for this practice! At the Beechcraft Training Center, we felt this was one area where the potential for engine harm was greater than the complete accuracy of the learning experience, so we kept about 20 inches of MP during our practice emergency descents in the Dukes and 58Ps. Even with that amount of power, they come downhill quite impressively!