STC'd Conversion Installs 1,000 SHP Garrett TPE-331 Engines,
By ANN Correspondent Juan Jimenez
How do you take one of the most successful business aircraft in
the history of aviation and make it better? You take the bull by
the horns and do it yourself.
That's what the Kilo Alpha 290 conversion does for the
Raytheon/Beechcraft King Air C90 and E90 series twin turboprop
aircraft. Two well-established leaders in the specialty aircraft
industry back the conversion. Murray Aviation is an operator of a
fleet of turbo-props and a designer/builder of airframe cargo
doors. National Flight Services is the largest independent
overhauler facility of TPE 331 engines with over 3,000 completed to
Mark Murray, co-owner of Murray Aviation, originally conceived
the conversion. Murray had a King Air A90 with PT6 engines, and an
MU-2 with TPE-331 engines. He considered the King Air to be
underpowered, the complete opposite of the MU-2, regarded by many
as the aviation equivalent of a thoroughbred race car. He decided
to combine the best of the two - a big wing on one, a big motor on
the other - and came up with the concept of upgrading the engines
on the King Air to improve its performance.
Garrett has invested significant time and effort into improving
their TPE-331 engine, which at one point was known in the industry
as the "Garrett Grenade." The engine selected for the upgrade is
the TPE-331-10AV-511KA, a 1,000 shp engine, de-rated to 715 shp for
the Kilo Alpha installation. Unlike the engine it is replacing, the
Garrett engine has double the TBO, a whopping 7,000 hrs.
The results in terms of performance are impressive. Initial
flight tests demonstrated 600 ft takeoff rolls. Setting power at
2,000 rpm at FL240 resulted in an impressive 285 kt cruise. Climb
performance is equally impressive. Between FL130 and FL190 the
aircraft can climb at a 2,000 fpm at 165-180 kts IAS. At 100% rpm
Murray's A90 was getting a 1,300 nm zero-wind range. Pull back to
economy cruise and that number increases to 1,500 nm. An upgraded
E90 results in 1,700 and 2,000 nm, respectively.
According to company documents, an analysis of operating costs
between a stock C90 and a Kilo Alpha 290 converted aircraft shows
that direct operating costs are dramatically improved as well.
Assuming a mission profile of 15 trips of 600 nm, 30 of 1400 nm and
25 of 1800 nm a year, engine reserve costs are reduced from $120 to
$52 and change. The biggest reason for this is the near doubling of
the TBO and engine midlife inspection cycles. Annual direct
operating cost savings is calculated at just over $73,000. The
numbers and charts the company is presenting to back up these
numbers are available on its website, listed below.
The conversion also includes the installation of a new
five-bladed McCauley noise reduction propeller using shorter blades
than the factory installed props. This has the effect of reducing
noise by reducing the tip speed of the prop blades to below
A new exhaust stack is also installed which redirects boundary
layer airflow and mixes it with the exhaust to virtually
eliminating the sooting King Air's are so well known to suffer
National Flight Services in Lakeland, Florida, has been selected
as the national installation service for the Kilo Alpha conversion.
National Flight has accumulated experience through the overhaul of
over 3,000 Garrett TPE-331 engines, the largest number of any
authorized overhauler. In addition to the engine conversion and
avionics upgrade, National Flight Services can also install
Raisbeck upgrades such as their Aft Body Strakes.
Currently, the conversions are being completed in approximately
10 weeks. Kilo Alpha and National Flight Services are working to
reduce the time to a total of 6 weeks.