20/Twenty

Fred George

Today, half a million dollars goes a long way in the used light jet market, give or take $100,000. That’s the going price for almost any one of the first-generation 1982 through 1985 Mitsubishi Diamond IA aircraft. The aircraft’s oval-shaped fuselage cross section affords passengers more head, shoulder and foot room than most other light jets because they have circular cross sections.

Powered by 2,500-pound-thrust Pratt & Whitney Canada JT15D-4 turbofans, the original Diamond I first flew in 1978, was certified in 1981 and entered service in 1982. Soon after, though, Mitsubishi developed the Diamond IA variant equipped with upgraded systems and fitted with -4D engines having improved high-and-high performance.

Early aircraft came equipped with Honeywell (nee Sperry) SPZ-900 flight guidance systems, SPZ-500 autopilots and Collins Pro Line I radios. Later models were fitted with Pro Line II radios and upgraded with several options, including UNS-1 FMSes, RVSM equipment, TAWS and TCAS.

Operators say the Diamond IA, with a weight boost mod, can fly seven travelers 1,000 nm in 2.5 hours and land with 100-nm NBAA IFR reserves. Its Mitsubishi-designed, super-critical airfoil with 20 degrees of sweep enables it to cruise efficiently 410 to 420 KTAS in the low to mid-thirties. First-hour fuel burn is 1,400 pounds, second hour is 1,200 pounds and during the third hour it decreases to 1,000 to 1,100 pounds.

Similar to many other aircraft, the Diamond gained considerable weight during development. Mitsubishi pegged its maximum takeoff weight at 14,630 pounds to keep its standard-day TOFL below 4,000 feet. However, its hefty 10,200- to 10,300-pound average BOW and a 4,255-pound maximum fuel capacity resulted in a one-passenger tanks-full payload. New Flight Corp.’s STC SA3891NM helps operators overcome that limitation by raising max ramp weight, MTOW and max landing weight. This restored the aircraft’s promised full-tanks, full-seats capability. But the weight boost mod also increases the aircraft’s runway requirements, a characteristic that can be challenging especially when departing hot-and-high airports. Weight-altitude-temperature limitations come into play at OATs of 80°F or warmer.

Warm days also can make a stock Diamond IA’s cabin uncomfortable on the ground. A popular upgrade is the Keith Products electrically powered, vapor-cycle air conditioner. Several operators also have fitted their aircraft with Lear Siegler starter-generators, Concorde lead-acid batteries and more accessible emergency standby battery systems to lower maintenance costs and increase reliability.

Some operators have elected to fit the aircraft with an auxiliary fuselage fuel tank that boosts range by 240 miles. However, the extra weight hurts runway performance.

Basic maintenance intervals are 200, 600, 1,200 and 2,400 hours for Phase A, B, C and D checks. The landing gear must be overhauled at 3,000 cycles, a $50,000 maintenance cost. Parts support through Hawker Beechcraft Corp., the current owner of the type certificate, is good and it’s getting better. The P&WC JT15D-4D engines have a 3,000-hour TBO and overhaul costs $500,000 to $650,000.

Notably, AD 2009-07-02 requires that Diamond IA operators upgrade the structure of the crew chairs, a modification that costs $24,500 in parts and requires 80 labor hours.

With such potentially heady maintenance costs, you may end up spending $1.5 million for a $500,000 airplane if you don’t do a very careful pre-buy inspection. Alternatively, you could part it out for $300,000 to $400,000.

There’s plenty of competition in the light jet market at present — lots of early 1980s models priced well below $1 million from which to choose. The Citation I, for instance, has considerably better runway performance for about $550,000 to $800,000, according to Lawson Brown, a broker at San Diego-based Aviation Unlimited. But it also has a smaller cabin and 70- to 80-knot slower cruising speeds. The Citation II also has better runway performance and a cabin that’s slightly longer, if not a touch smaller in cross section. It commands $700,000 to $1.2 million at resale time. The Learjet 35 also can be purchased for $700,000 to $1.5 million. It has a much smaller cabin, but it can fly nearly twice as far, at much higher altitudes and cruise at faster speeds.

So, if you’re in the market for an entry-level jet with an accommodating cabin, 400-plus-knot cruise speeds and bedrock reliability, but not one with stellar runway performance, the Diamond IA may be worth considering. If you locate a well-maintained and upgraded airplane, it may prove to be quite a bargain.