Avweb.com wrote:Cessna to Offer Diesel Skyhawk
October 4, 2007

by Russ Niles
Editor-in-Chief

Cessna will offer the 172S Skyhawk with a Thielert turbo diesel engine with deliveries to start in mid-2008. In an announcement at AOPA Expo in Hartford, Conn., Cessna officials said the decision to offer the diesel came after extensive market surveys and flight testing. "The Skyhawk is already the best-selling, most-flown airplane ever with more than 43,000 delivered and this option further expands the market due to the worldwide availability of Jet A fuel," said John Doman, Cessna vice president of propeller aircraft sales. Cessna will install the engines at its Independence, Mo., factory under the supplementary type certificate already held by Thielert.

The engine is a two-liter adaptation of a Daimler automotive diesel that's been re-engineered for aviation use. It's a dual overhead cam, in-line four-cylinder engine that puts out 155 hp. It comes with full authority digital engine control and is turbocharged. The liquid-cooled engine drives a three-bladed, composite constant speed prop. The new designation of the aircraft is the Skyhawk TD. A Cessna news release did not contain pricing information.

SMA wrote:WARNING: FLIGHTS WITH OUTSIDE TEMPERATURE BELOW –5°C FROM SEA LEVEL TO 7500 FT AND OUTSIDE TEMPERATURE BELOW ISA-5°C ABOVE 7500 FT ARE STRICTLY FORBIDDEN.

DeltaHawk wrote:Q: In a diesel cycle engine air is compressed in cylinders and then fuel is injected into this hot air. For this reason, at high altitudes, thin and cold air results in restart problems. How have you overcome this?

A: You are correct to be concerned about high altitude restart capability in diesel cycle engines. At some critical altitude, de-spooling of the turbocharger by reducing fuel flow (reducing "throttle") can result in not enough heat of compression to ignite the fuel. Advancing the fuel lever will not restart the engine until the aircraft descends to a lower altitude where the air is denser. There are several approaches to mitigate this phenomenon. One is to use a higher compression ratio to raise the critical altitude. Another is to limit fuel flow excursions by imposing a controller between the fuel lever and the engine fuel pumps. It would control fuel based on atmospheric pressure and fuel lever position (an aneroid-based system). Liquid-cooled engines with thermostatic control help to keep the engine and thus the air supply warm, improving ignition properties. Catalytic "hot spot" approaches may work to maintain ignition below normal uncatalyzed ignition effective compression ratios. A mechanical supercharger driven by the windmilling propeller can provide additional charge density. Without getting too detailed, we use some of the above methods to raise our ignition critical altitude above that where most general aviation aircraft fly. Until we complete flight testing we cannot give a precise altitude, but we expect it to be above 30,000 ft (~9,240 m). We have demonstrated shutdown and restart with a non-windmilling propeller at 14,000 feet.

a64pilot wrote:............. Has the no overhaul thing been addressed?

maules.com wrote:According to SMA, the SMA 305 in the Maule has 2000 hours between overhaul at present with the goal being 3000 hours.
It has 585 less parts than equivalent hp gas engines, has 230hp, is turbocharged, runs at 2200rpm and burns 7.9 gph at 65% power of JetA and JetA1.
Jeremy

zero.one.victor wrote:So what are these diesel airplanes gonna burn-- highway diesel,Jet A, or what?