The Sling 4 TSi - N208RW

We spent a lot of time trying to determine which airplane would best suit our purposes for our around the world adventure. We spent a considerable amount of time at the Earthrounders Web site, seeing what others flew for their successful trips, and back in 2012 we traveled to Sun N Fun in Florida and attended the Earthrounders bi-annual meeting to talk to members of the group. We came away with a tremendous amount of highly relevant information.

Range

Typical general aviation aircraft have range capabilities of between 500 and 1000 nautical miles with full fuel. That can be enough to get you around the world, but it generally means that you are going to have short stage lengths, that limit where you can go and what you can see. The most common route will be from the U.S. to Newfoundland to Greenland, Iceland and the U.K. to cross the Atlantic, and then up through Russia and across the Aleutians to Alaska for the Pacific. Not a route you want to take in Winter. Now, you can take that standard typical aircraft and get a 10% to 20% over gross ferry permit and put a big fuel tank where the rear seats would normally go, and significantly extend your range. However, getting the tanks built to spec, installed and then securing and maintaining the permits is a relatively costly and time consuming process. Still, its how the majority of Earthrounders do it.

Payload

Then there is the whole gross weight issue - the carrying capacity of the airplane. Unfortunately, it is a truism in aviation today that you simply cannot put full fuel in the plane and fill every seat in the aircraft and be legal when you take off. Fill most planes with full fuel and you’ll be lucky if you can fill half the seats. A lot of Earthrounders have done solo circumnavigations, but when you put someone else in the right seat you have to leave precious fuel behind equivalent to compensate for the weight of the person you are carrying. And lets not forget you need lots of safety gear & supplies; a life raft, portable water maker, immersion suits, spare engine oil, sat phone, EPIRB, food and water, clothes, etc.

Aircraft Type

To qualify to become an Earthrounder you need to do the circumnavigation in a “light” aircraft, which by definition weighs less than 12,500 lbs (you could actually qualify in an early Lear Jet). Most make the trip in aircraft that weigh considerably less than half of that. Some few make the trip in turbine powered aircraft at relatively high altitude (>25,000 ft) and high speed (>250 knots). These planes are over our budget for this adventure and for us, a critical part of the trip is seeing what’s out there. We’ll be able to fly “low and slow” when necessary with good efficiency and our normal cruise altitudes will be 8,000 - 12,000 feet, although we’ll be able to go as high as 23,000 feet when necessary. The RV-10 is also a great short field aircraft and can get in and out of smaller strips when normally loaded. This adds a tremendous number of potential airfields to the route. And since exploring is a good part of what the trip is all about, for us this is important.

Fuel Type

This might seem like a non-issue, but there is a very real problem in securing avgas (100LL) for refueling. The LL in 100LL stands for low lead. The lead is used to prevent detonation and has been the standard fuel for general aviation aircraft for many, many years. Even though the lead levels are very low and do not at all increase lead levels in the atmosphere environmentalists, long on emotion and low in common sense, have taken issue with its very existence.  100LL is produced by few suppliers and in very limited quantities compared to auto gas, and so the fuel is expensive, typically more than $2 per gallon more than auto gas in the U.S., and small isolated communities can charge what they want. A recent Earthrounder who stopped in Dubai for fuel was charged over $20 per gallon.

Price is one thing, but complete lack of availability is a worse problem. At some South Pacific stopovers and virtually all of Russia you have to arrange to have the fuel shipped in, in advance, and some Pacific Islands won’t even allow it to arrive in barrels on cargo vessels, fearing liability. So, if you are flying a conventional general aviation aircraft powered by a reciprocating engine, you have to give serious planning to fuel availability. Starting to plan a year in advance for fuel shipping is not unusual. This is where the Sling 4 TSi has an advantage because the turbocharged Rotax 915 iS is able to burn auto-fuel which is available almost everywhere. Ideally, Premium is best, but regular can be used with an octane booster additive.

This is one area where jets and turbines have an advantage, as Jet A fuel is available just about everywhere there is a fair sized airport. But, you’ll pay $1 million or more for the aircraft, and because turbines are inefficient at low altitude you’ll be flying at high altitude and at high speed - not seeing much. Liz and I seriously considered a Socata TBM 700c2 which with an over-gross permit could barely make the trip from California to Hawaii. In the end, we decided it was not the type of flying we wanted to do.

There is a solution to the problem, but it is a rare one at the moment. There are several manufacturers trying to produce and certify diesel aircraft engines between 135 and 300 HP. New light weight alloys that can withstand a diesel’s high compression ratio are being used, and with turbocharging and after-cooling the weight per HP is basically the same as conventional gas aircraft engines when gearboxes and accessories are considered. These engines will burn either diesel of jet fuel, so they can be refueled anywhere. And even though diesel weighs a pound more per gallon than avgas, the specific fuel consumption (e.g. economy) is much better with a diesel so you can go considerably farther with the same weight of fuel. Cessna and Mooney have recently dropped diesel powered aircraft development programs and Continental is unwilling to support the use of their diesel powered engines in Experimental Aircraft because the effort requires too much installation support. Right now, the only viable proven alternatives are the Diamond DA-42 VI at about $1 million and the Diamond DA-62 VII at $1.5 million. These are both twin engine aircraft with twice the complexity and much higher operating costs.

Safety

It goes without saying that we wanted an aircraft that was proven to be safe in operation. We briefly considered twin engine aircraft, the certificated Diamond models with twin diesels being the most obvious choice in this category. In the end, the expense of twin engines and their fuel consumption and their added complexity was deemed not worthwhile given the incredible reliability of contemporary aircraft engines once fuel contamination is ruled out. Bad fuel will kill two engines as quickly as one. As someone once famously said, “the second engine will carry you a bit further to the crash site.”

Moreover, much of the important safety capability can be added with additional equipment. Such things as an angle of attack meter, HF radio, sat phone, a glass cockpit with synthetic vision, de-icing equipment, airframe parachute system, etc.

Possible Aircraft

We focused on four conventional certificated aircraft that could do the job. They would carry two of us and all our belongings and equipment and have a 2500 nm range when equipped with ferry tank(s). They would be affordable to purchase and to refit with the equipment above. They would all require ferry permits. On our list:

1. 1)A-36 Bonanza with Dolly Parton tip tanks (100 gal each)
   

2. 2)Mooney Ovation GX2
   

3. 3)Cessna 210 Centurion
   

4. 4)TBM 700c2 (turbine powered burning Jet-A)
   

5. 5)Ravin 500 from South Africa.
   

There were advantages and disadvantages for each choice, but ultimately we decided to go with an unconventional solution to the problem.

A Fully Equipped, Custom Built Sling 4 TSi powered by a Rotax 915iS

South Africa’s The Airplane Factory builds kit planes. They are relatively new to the market and have 200+ aircraft flying. They build the Sling 2 Light Sport and the Sling 4 powered by a Rotax 912 and the Sling 4 TSi. They have great performance attributes and are every bit as capable as their certificated brethren, if not more so. And, they have the added advantage of costing about half as much (or less) as a certificated general aviation aircraft of similar size and capability.

The Sling 4 TSi is a four place aircraft with fixed gear and constant speed controllable prop. The Rotax 915iS is single lever FADEC controlled turbo charged and after cooled and has a critical altitude of 16,000 feet. This means it will generate 100% power to 16,000 feet where a conventional non-turbo, normally aspirated engine would only make about 50% power at that altitude. Unlike virtually any other aircraft in its class it has a full fuel standard configuration to fill the tanks, all four seats with adults, and legally go flying.

Is there a stigma associated with flying a “kit plane?” (Experimental, Amateur Built or E-AB). Perhaps. Two places, Singapore and Japan don’t like them and won’t let them fly in their air space. But, they outsell conventional general aviation aircraft in the U.S. by a wide margin and in many cases the final quality is a product of a tremendous amount of time and effort lavished on their construction that simply cannot be met with an assembly line built certificated counterpart. The requirement for the E-AB designation is that the aircraft be 51% built by the builder and that it not be used for commercial purposes, but E-AB aircraft can fly at night and in instrument conditions (even in known icing) if properly equipped.

Building an E-AB aircraft has several benefits. First for our purposes is that the builder certifies the gross weight, so the aircraft can be built and certified with the auxiliary fuel required and no over gross/ferry tank permits are necessary. Second, you can build the aircraft to your exact requirements and equip it precisely the way you want it with all the latest and greatest bells and whistles. This is an important consideration when doing an RTW trip and flying in isolated areas with unregulated air space and a wide degree of varying conditions.  One of these advantages is a full airframe parachute system.

The Airplane Factory

The Sling 4 TSi is built by The Aircraft Factory in South Africa. Our aircraft will be assembled at their U.S. Headquarters at Zamperini Field in Torrance, California. The company’s principals have flown both a Sling 2 and a Sling 4 around the world and they have offered their full support for our RTW effort. They have gone to significant effort to make sure that our aircraft is fully equipped for the undertaking, including built in auxiliary tanks that will bring the total fuel capacity to approximately 155 gallons. They have confirmed we will be able to certify the aircraft for its full up gross weight, meaning no ferry permits will be required. The aircraft will also be equipped with a full airframe ballistic parachute system.

Equipment is Critical

Our Sling 4 TSi, N208RW (our area code and RW for around the world) will be well equipped for the task. Non standard equipment will include (list in development):

Garmin G3X x2 glass cockpit with synthetic vision and EMS

GTS 800 Active Surveillance Traffic System

Garmin GTN 750 Navigator

Garmin GSR 56 Satellite Comm w/tracking & sat weather

Garmin GTR20 remote comm radio

Electronics International FP-5L-60 fuel totalizer

XM weather and BF Goodrich WX-500 Stormscope

Garmin GTX 45R Transponder

Garmin Autopilot

Garmin GEA 24 Engine Monitoring System

Back up primary instruments

Emergency power generation capability

Angle of attack indicator

Magnum ballistic parachute system

Known ice anti-icing capability

Supplemental oxygen system

HF radio

ELT, EPIRB, SPOT, Portable GPS

Carbon monoxide monitor

Pulse oximeter

Ditch bag, survival suits where necessary, survival kits as necessary

iPad with flight management software x 2