Story ID: 331Ikhana STC
Heavier Twin Otter STC Expected in 2016
By: Chris Kjelgaard
Caption: The high-gross-weight modification of the venerable Twin Otter is Ikhana’s latest project.
Word Count: 1039
NBAA exhibitor Ikhana Group (Booth N4410) expects the FAA to award it a supplemental type certificate (STC) in the first half of 2016–and perhaps as early as the first quarter–for its new high-gross-weight “HG” modifications for Twin Otter Series 300 and 400 models.

Ikhana’s DHC-6-300HG and DHC-6-400HG mods–as the company refers to them–are intended to allow maximum takeoff weight (mtow) increases of 1,500 pounds for the de Havilland Canada Twin Otter 300 and the Viking Air 400, under standard airworthiness certification. The increase would give each model a 14,000-pound mtow for standard-category operations, including all passenger flights.

John Zublin, Ikhana’s president and CEO, said the company, which does business as Ikhana Aircraft Services, expects to obtain its DHC-6-300HG and Viking Air DHC-6-400HG STCs “in the first part of next year, subject to FAA” timing.

Using a Twin Otter 300 it owns, Ikhana already has performed “a substantial amount” of test flying of the DHC-6-300HG mod to FAA standards, “as much as the OEM [would have done], or more so,” according to Zublin. Now, he added, “We’re getting ready for the FAA flight tests.” Ikhana is concurrently pursuing Transport Canada certification.

Although de Havilland Canada manufactured the Twin Otter 300 (rolling out the last one in 1988) and Viking Air builds the Series 400 (delivering the first example in 2010), Ikhana expects to be able to cover both models with one STC.

The Series 300 is powered by Pratt & Whitney Canada PT6A-27s, each rated at 620 shp. But while the Series 400 is powered by PT6A-34s (normally rated at 750 shp), Viking production Series 400s are powered by PT6A-34s de-rated to 620 shp. This is why both Twin Otter models have standard-category certification to 12,500 pounds mtow.

Payload Increase

Ikhana’s HG mod replaces 620-shp-rated PT6A-27s or PT6A-34s with fully rated PT6A-34s, each delivering 750 shp. The 130-shp “horsepower bump” per engine enables the 1,500-pound payload increase, which operators could use in many ways, according to Zublin. “Operations on floats, we see a huge market for that,” he said. The mtow increase would more than offset the extra weight of the float pontoons, allowing operators of Twin Otter amphibians or floatplanes to carry full payloads of passengers and bags more often.

“We also think those operators not on floats always have a fuel-staging problem, even on fixed gear,” added Zublin. “This allows them to do their [operations] planning in a different way.”

Additionally, operators serving tourist destinations may find the mtow increase valuable because “passengers are getting heavier, so the HG [mod] gives you the ability to have more people on the aircraft without leaving seats vacant,” according to Zublin. “It’s also how much baggage they haul.” Some passengers tend to bring a lot of baggage on vacation.

Ikhana already performs a similar mod, but the STC it holds was granted only for restricted-certificate flying on special-missions or cargo-only operations. For the past four years Ikhana has held a Twin Otter 300/400RG STC, which gives both models a 14,000-pound mtow for restricted-category operations.

“So far there are 22 to 23 aircraft in service worldwide” modified with the RG STC, said Zublin. However, Ikhana’s RG and HG mods for the Twin Otter 300 and 400 are by no means identical. “It’s not a plug-and-play [mod] at 14,000 pounds standard category,” he explained. “The restricted-category [mod] is much easier; it involves minimal changes to the aircraft.”

Ikhana also offers Twin Otter 100/200HG mods–using PT6A-27s rated at 620 shp–which increase the mtow of these earlier DHC-6 models to 12,500 pounds, like that of the Twin Otter 300 and 400. However, because the DHC-6 100 and 200 each have an empty weight of 7,200 pounds whereas the Series 300 and 400 each weigh 7,500 pounds empty, Zublin said some operators prefer HG-mod Twin Otter 100s and 200s over the later models, because they offer 300 pounds more payload capability.

Now, Ikhana is pursuing a new mod that, if granted an STC, would allow Twin Otter 300s to operate special missions at an even higher (but unspecified) mtow than would its planned HG mod for Series 300s and 400s.

Under what Ikhana calls its “Harbinger Program,” it is also working with GE Aviation to re-engine one of its own Twin Otter 300s with two GE H85 engines, each rated at 850 shp. The company expects to fly the prototype in 2016. “We’re well into design and planning,” said Zublin. “Our goal is to have a viable prototype by the middle of next year.”

In special missions, such a mod would also be valuable for providing additional aircraft power, electrical power and loiter capability, according to Zublin. “For special missions you can never have enough power.”

Ikhana also offers four re-lifing STCs for Twin Otter 200s and 300s and a wing life-extension STC (to 35,000 hours/70,000 cycles) for Series 100s.

The Series 200/300 re-lifing STCs–any of which customers may select individually, or choose to combine in various ways–can culminate in Ikhana’s Twin Otter X2. This is a Twin Otter 200 or 300 the company has purchased and re-lifed using all four Series 200/300 STCs to nearly new condition.

Fresh from Ikhana, Twin Otter X2s offer 66,000 hours/132,000 cycles of certified fuselage life and 45,000 hours/90,000 cycles of wingbox and nacelle life. Aircraft delivered new by de Havilland Canada offered the same limits. Each X2 also has a new interior, new engines, customized avionics and all-new wiring. Ikhana lists the X2 at $5.2 to $5.3 million.

The company is now working on its second X2 and its fourth 66,000-hour/132,000-cycle fuselage re-lifing. Ikhana has held its wing-box re-lifing STC since 1996, when the company was known as R.W. Martin, and has re-lifed some 130 wing-boxes on 115 aircraft. Now Ikhana is performing 10 to 12 wing-box re-lifing mods annually, said Zubin.

Ikhana is showcasing all these products and its Twin Otter air conditioning mod at NBAA 2015, as well as its array of special-missions products and modifications for dozens of different aircraft platforms. These range from the Grob G 520 Egrett to the Boeing 747.