Diamond DA42 Twin Star

The Diamond DA42 Twin Star, introduced in 2004, is a revolutionary aircraft — the first certified twin to use diesel/jet fuel engines. Powered by two Austro Engine AE 300 turbodiesel engines (170HP each), the DA42 burns approximately 10 GPH total — less than many single-engine aircraft and roughly one-third of what a conventional piston twin like the Baron consumes.

The DA42 has become the standard multi-engine trainer worldwide, used by flight schools, military academies, and university aviation programs. Its combination of twin-engine safety, diesel fuel economy, composite construction, and Garmin G1000 avionics makes it the modern benchmark for multi-engine training.

Early DA42 models used Thielert TAE 125 engines, which had serious reliability problems leading to Thielert's bankruptcy. Diamond developed the Austro AE 300 as a replacement, which has proven significantly more reliable, though Austro engines have still experienced notable ADs and parts availability challenges.

The DA42 remains in production. New DA42-VI models list at approximately $1,000,000+. Over 1,200 DA42s have been produced.

The DA42-VI cruises at 180 KTAS on only 10 GPH total (Jet-A fuel). This is remarkable — a Baron 58 cruises at 200 KTAS but burns 30 GPH of avgas. The DA42's fuel cost per hour is approximately 60% less than a conventional piston twin.

The FADEC-managed diesel engines operate on Jet-A/Jet-A1 fuel, which is available worldwide and typically cheaper than 100LL avgas. The engines also have a TBO of 1,800 hours.

Single-engine performance is a DA42 strength — the composite airframe's low drag means single-engine climb rate is positive even at gross weight in most conditions. This is a significant safety advantage over conventional light twins.

DA42-VI (2× AE 300, 340HP total, 50 gal Jet-A fuel):

The DA42's 1,069 lbs useful load is modest for a twin, but the extraordinary fuel efficiency (10 GPH total for 50 gallons) provides exceptional range. Two adults with full fuel have 1,100 nm range — extraordinary for any twin, let alone one burning 10 GPH. Four adults requires fuel management for practical baggage.

• Flight Training (8): THE multi-engine trainer of the modern era. Used worldwide for multi-engine ratings. Low fuel burn makes training economics practical. Excellent single-engine performance for training scenarios.
• Backcountry (1): Not applicable.
• Business Travel (6): 180 KTAS, IFR capable, four seats. Adequate for moderate business travel but limited by the small cabin and 1,069 lbs useful load.
• Aerobatics (1): Not certified.
• Cross-Country (7): 1,100 nm range on 10 GPH is extraordinary efficiency for a twin. 180 KTAS is respectable. Good cross-country capability limited by cabin size.
• Cargo Hauling (3): Small cabin, limited useful load for a twin.
• Local Fun Flying (4): Burning twin-engine fuel for local flying isn't economical. The DA42 exists for training and cross-country missions.
• Surveying (6): Excellent platform — twin-engine redundancy, efficient fuel burn for long endurance (10+ hours theoretical), and good slow-flight characteristics. Used for aerial survey operations.

• Early DA42 (Thielert): Basic Garmin G1000 or Avidyne Entegra.
• DA42 NG / DA42-VI: Garmin G1000 NXi standard. FADEC integration provides engine management through the glass cockpit. Comprehensive IFR capability.

Extremely limited — integrated composite/diesel system:

• Engine conversions: Some Thielert-equipped DA42s have been converted to Austro AE 300.
• The DA42 is a fully integrated system with essentially no aftermarket modification options.

• Annual inspection: $3,000-$6,000. Austro engine inspections add to baseline.
• Engine overhaul: $35,000 per Austro AE 300 ($70,000 total). Lower than conventional piston twins but parts availability can delay overhaul scheduling.
• Austro-specific maintenance: Requires Austro-authorized service centers. Not every A&P shop can work on diesel aircraft engines.
• Diamond service network: Active worldwide but Austro engine service is the bottleneck.
• Annual all-in cost: $25,000-$40,000 depending on utilization. Fuel cost advantage partially offset by higher engine maintenance costs.
• Operating cost: $120-$160/hour all-in — significantly less than conventional piston twins at $250-$350/hour.

• DA42 (Thielert, 2004-2008): $250,000-$350,000. Significantly discounted due to engine support.
• DA42 NG (Austro, 2009-2012): $350,000-$550,000.
• DA42-VI (Austro, 2013+): $500,000-$1,100,000.

Per valuation-methodology: Engine type (Thielert vs Austro) is the primary value differentiator. Thielert-equipped aircraft are dramatically less valuable. Engine time on Austro engines ($35,000 per engine overhaul = $70,000 total) is critical.

Key Concerns:

• Austro AE 300 ADs: The Austro engines have experienced a series of significant ADs including piston-related ADs requiring immediate inspection. Some ADs have been severe enough to ground aircraft until compliance.
• Thielert TAE 125 (early models): Engine support effectively ended when Thielert went bankrupt. These engines have mandatory replacement/conversion deadlines.
• Parts availability: Austro engine parts can have significant lead times (4-6 weeks for some components). This is the #1 operational concern for DA42 owners.
• Castering nosewheel: Same differential braking requirement as DA40.
• Composite repair: Standard composite concerns.
• Fuel system: Diesel fuel system requires specific maintenance procedures different from avgas systems.

Per insurance-underwriting:

• Hull insurance: $4,000-$7,000/year. Twin-engine rates, but the DA42's excellent safety record helps.
• Pilot minimums: Multi-engine rating, 200+ hours total. Training operations covered through fleet policies.
• The DA42's safety record is among the best in its class.