Category Archives: Aviation

Solar Impulse 2 is Making its way Across the USA

Peter Lobner

If you have been reading the Pete’s Lynx blog for a while, then you should be familiar with the remarkable team that created the Solar Impulse 2 aircraft and is attempting to make the first flight around the world on solar power.  The planned route is shown in the following map.

Solar Impulse 2 route map

Image source: Solar Impulse

I refer you to my following posts for background information:

  • 10 March 2015: Solar Impulse 2 Designed for Around-the-World Flight on Solar Power
  • 3 July 2015: Solar Impulse 2 Completes Record Solo, Non-Stop, Solar-Powered Flight from Nagoya, Japan to Oahu, Hawaii
  • 27 February 2016: Solar Impulse 2 Preparing for the Next Leg of its Around-the-World Journey

Picking off where these stories left off in Hawaii, Solar Impulse 2 has made four more flights:

  • 21 – 24 April 2016: Hawaii to Moffett Field, near San Francisco, CA; 2,539 miles (4,086 km) in 62 h 29 m
  • 2 – 3 May 2016: San Francisco to Phoenix, AZ; 692 miles (1,113 km) in 15 h 52 m
  • 12 – 13 May 2016: Phoenix to Tulsa, OK; 976 miles (1,570 km) in 18 h 10 m
  • 21 – 22 May 2016: Tulsa to Dayton, OH; 692 miles (1,113 km) in 16 h 34 m

From the above distances and flight times, the average speed of Solar Impulse 2 across the USA was a stately 43.6 mph (70.2 kph).  Except for the arrival in the Bay Area, I think the USA segments of the Solar Impulse 2 mission have been given remarkably little coverage by the mainstream media.

SI2 flying above the USAImage source: Solar Impulse

Regarding the selection of Dayton as a destination for Solar Impulse 2, the team posted the following:

“On his way to Dayton, Ohio, hometown of Wilbur and Orville Wright, André Borschberg pays tribute to pioneering spirit, 113 years after the two brothers succeeded in flying the first power-driven aircraft heavier than air.

To develop their wing warping concept, the two inventors used their intuition and observation of nature to think out of the box. They defied current knowledge at a time where all experts said it would be impossible. When in 1903, their achievement marked the beginning of modern aviation; they did not suspect that a century later, two pioneers would follow in their footsteps, rejecting all dogmas to fly an airplane around the world without a drop of fuel.

This flight reunites explorers who defied the impossible to give the world hope, audacious men who believed in their dream enough to make it a reality.”

Wright Bros and SI2 pilotsImage source: Solar Impulse.

You can see in the above route map that future destinations are not precisely defined. Flight schedules and specific routes are selected with due consideration for en-route weather.

The Solar Impulse 2 team announced that its next flight is scheduled to take off from Dayton on 24 May and make an 18-hour flight to the Lehigh Valley Airport in Pennsylvania. Following that, the next flight is expected to be to an airport near New York City.

If you haven’t been following the flight of Solar Impulse 2 across the USA, I hope you will start now. This is a remarkable aeronautical mission and it is happening right now. You can check out the Solar Impulse website at:

If you wish, you can navigate to and sign up for e-mail updates on future flights. Here’s the direct link:

With these updates, you also will be able to access live video feeds during the flights. OK, the videos are mostly pretty boring, but they are remarkable nonetheless because of the mission you have an opportunity to watch, even briefly, in real time.

There’s much more slow, steady flying to come before Solar Impulse 2 completes its around-the-world journey back to Abu Dhabi. I send my best wishes for a successful mission to the brave pilots, André Borschberg and Bertrand Piccard, and to the entire Solar Impulse 2 team.

Solar Impulse 2 Preparing for the Next Leg of its Around-the-World Journey

Peter Lobner

In my 10 March 2015 post, I provided basic information of the remarkable Solar Impulse 2 aircraft and its mission to be the first aircraft to fly around the world on solar power. On 10 July 2015, I posted a summary of the first eight legs of the around the world flight, which started in Abu Dhabi on 9 March 2015 and ended on 3 July at Kalaeloa, a small airport outside Honolulu, Hawaii.

After arriving in Hawaii, the Solar Impulse team determined that the batteries had been damaged due to overheating on the first day of the Leg 8 flight and would have to be replaced. Solar Impulse reported the following root cause for the overheating:

“Since the plane had been exposed to harsh weather conditions from Nanjing to Nagoya, we decided to do a test flight before leaving for Hawaii. Having to perform a test flight followed by a mission flight had not been taken into account in the design process of the battery system, which did not allow the batteries to cool down in between the two” (flights).

By November 2015, the Solar Impulse engineers had upgraded the design of the whole battery system and integrated a battery cooling system. You can read the details on the Solar Impulse website at the following link:

A further delay in starting Leg 9 was caused by the seasonal shortening of daylight hours in the Northern hemisphere. The late autumn and winter daylight hours weren’t long enough to allow the batteries to be fully recharged during the day along the planned route to the U.S. mainland and back to Abu Dhabi.

Solar Impulse 2 routeSource: Solar Impulse

On 26 February 2016, the upgraded Solar Impulse II made a successful “maintenance” flight in Hawaii. The flight lasted 93 minutes, reached an altitude of 8,000 feet (2,400 meters), and included tests of the stabilization and battery cooling systems.

Solar Impulse is planning to restart its around-the-world journey on 20 April 2016.

Solar Impulse composite photo over HawaiiSource: Solar Impulse

You can subscribe to news releases from the Solar Impulse team at the following link:

The Complexity of a WW II P-47 Thunderbolt’s Powerplant

Peter Lobner

The P-47 Thunderbolt, built by Republic Aviation, was a powerful WW II fighter that was capable of operating effectively at high-altitude as a long-range bomber escort or at low altitude as a fighter bomber. That tactical flexibility was enabled by its turbocharged Pratt & Whitney Double Wasp R-2800, two-row, 18-cylinder radial engine. A representative P-47D is shown in the following photo.

P-47D_DSC09072Source: Author photo

Basic specifications for a P-47D are listed below (Source: National Museum of the USAF):

  • Engine: One Pratt & Whitney R-2800 radial rated at 2,430 hp
  • Maximum speed: 433 mph
  • Cruising speed: 350 mph
  • Range: Approx. 1,100 miles with drop tanks
  • Ceiling: 42,000 ft.
  • Armament: Eight .50-cal machine guns and 2,500 lbs. of bombs or rockets
  • Span: 40 ft. 9 in.
  • Length: 36 ft. 2 in.
  • Height: 14 ft. 8 in.
  • Weight: 17,500 lbs. maximum

The basic engine installation can be seen in the following illustration of a P-47 without its engine cowling:

P-47 no engine cowlingSource:

The R-2800 engine is turbocharged, with the turbocharger, intercooler, and related subsystems all located behind the pilot. There is a lot of intake ductwork needed to get ambient air routed from the main air duct intake immediately under the engine to the turbocharger and intercooler and then back to the carburetors on the engine.

  • The air entering the turbocharger is compressed and, in the process, is heated. This air passes through the intercooler where it is cooled before being directed back to the engine and the carburetors for each of the 18 cylinders.
  • The air entering the intercooler cools the compressed air from the turbocharger’s compressor and then is discharged through exit doors on the sides of the P-47 fuselage, aft of the pilot.

Similarly, there is a lot of exhaust system ductwork needed to collect the exhaust from 18 cylinders into tailpipes and then route it back to drive the turbine section of the turbocharger and then be discharged via the main exhaust on the bottom of the P-47 fuselage.

These basic intake air and exhaust flow paths are shown in the following diagram.

P-47 powewrtrain_DSC_5382 cropSource: National Museum of the USAF

While visiting the National Museum of WW II Aviation in Colorado Springs, CO, I saw the complete P-47 powertrain shown in the following photo. The engine is at the extreme left, the turbocharger is at the extreme right, and the intercooler is at the point where the carburetor air duct (top) converges in a “V” with the main air duct (bottom). The darker exhaust tailpipes flank the main air duct along the bottom of the powerplant.

P-47 powertrain_DSC_7265-66 panoSource: Author photo

From the front, the Pratt & Whitney R-2800 dominates the view in the following photo. The main air duct intake is visible under the engine. The carburetor air duct (top), and the main air duct and darker exhaust tailpipe (bottom) are visible to the left, behind the engine.

P-47 powertrain_DSC_7258Source: Author photo

From the back of the powerplant, the turbocharger dominates the view in the following photo. As shown by the arrows, intake air enters the compressor section of the turbocharger from the top (grey arrow) and exits via the volute (red arrow), headed for the intercooler. The darker exhaust tailpipe can be seen connecting to the turbine secion of the turbocharger (below the red arrow) and exhausting under the turbocharger (yellow arrow).

P-47 powertrain_DSC_7262Source: Author photo

The following photo shows more clearly the connection of the exhaust tailpipes to the turbine section of the turbocharger and the exhaust point from the turbine section (beneath the P-47’s fuselage). Also shown is the intercooler, which is a heat exchanger that receives cool ambient air from the main air intake duct and warm, compressed air from the turbocharger’s compressor discharge (red arrow). After cooling the compressed air headed for the carburetors, the intercooler exhausts through rectangular ducts on the sides of the P-47 (yellow arrow).

P-47 powertrain_DSC_7260Source: Author photo

A better view of the intercooler exhaust duct (one of two) is shown in the following photo.

P-47 powertrain_DSC_7268Source: Author photo

So there you have it. While the P-47 looks bulky , this is largely due to the use of a big radial engine plus all of the ductwork, intercooler and turbocharger hardware packaged inside the fuselage.