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XB-70 Valkyrie and Flight Test of Jet Engines on Surrogate Aircraft – Airplanes by Design

February 22, 2012 in Airplane with 0 Comments

The XB-70 was a Mach 3.0 aircraft and noted by NASA to be the world’s largest experimental aircraft.

XB-70 NASA photo 359356main_ECN-792_full

This view shows both the engine inlets themselves and the shape of the fuselage that houses the inlets leading to the intakes of each of its six engines.

XB-70 NASA photo 359284main_EC68-2101_full

Here is an exhaust view of the six GE YJ93 engines.

Often jet engines in development are flown on surrogate aircraft. The GE YJ93 was first flown on a B-58 at Edwards AFB, as seen here.
B58 with j93 pod for engine flight test

The XB-70 boasted some other unique design characteristics, including its use of compression lift and the ability to droop its wingtips to increase directional stability. For a detailed project description of the XB-70 program see NASA’s website here.

Airplanes by Design features photographs of aircraft from a test pilot perspective, highlighting aeronautical engineering characteristics and flight test facts. To see all of the these pictures (and many more of this aircraft and it’s unique design characteristics), click here. You will always be able to access any of these pictures by selecting the Flickr icon in the top menu bar.

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Engine Design for VTOL: Hawker Siddeley XV-6A Kestrel – Airplanes by Design

February 15, 2012 in Airplane with 2 Comments

The Hawker Siddeley XV-6A at the National Museum of the Air Force illustrates two more characteristics of aircraft engines in Vertical Takeoff and Landing (VTOL) aircraft, continuing the February ABCs of aircraft engines series.

Inlet
The engine inlet is a marvel of aerodynamic engineering used to recover as much total pressure as possible while slowing the incoming air to an efficient speed for the engine.
HAWKER SIDDELEY XV-6A KESTREL
Additionally, engine inlets have to provide some mission design functions, like stealth characteristics, and they have to work at a wide variety of speeds, including both subsonic and supersonic flight regimes.

Nozzle
The purpose of the jet engine nozzle is to accelerate hot gases by adiabatic expansion.
XV-6
In the case of this Harrier forerunner (and some modern jets), the purpose was also to vector thrust for added control. Modern transport aircraft also vector thrust with thrust reversers during landing for deceleration.

These pictures were generously shared by Jason C. from his visit to the USAF’s National Museum.

Airplanes by Design features photographs of aircraft from a test pilot perspective, highlighting aeronautical engineering characteristics and flight test facts. To see all of the these pictures (and many more of this aircraft and it’s unique design characteristics), click here. You will always be able to access any of these pictures by selecting the Flickr icon in the top menu bar.

Click here to read more about this airplane.

Send a message to @FlightTestFact on Twitter to share your Airplanes by Design stories and photos.

3 Characteristics of Turbine Engines: F-15 C/D Eagle — Airplanes by Design

February 8, 2012 in Airplane with 1 Comment

This week continues the ABCs series by introducing three characteristics of aircraft turbine engines–afterburner, bypass ratio, and compressor–with an Edwards AFB F-15C/D Eagle as the example.
McDonnell Douglas F-15C/D Eagle

Afterburner
McDonnell Douglas F-15C/D Eagle
This is the afterburner section of the F-15.

F100 engine Pratt and Whitney cutaway drawing
This Pratt and Whitney drawing shows a cutaway of the F100 engine, in use on the F-15. The aft section (which appears orange in this drawing) is the afterburner section where fuel is ignited.

Bypass Ratio
A certain amount of air goes around the jet engine core. The ratio of air that bypasses the core to that air that goes through the core is the bypass ratio. If you look closely at the drawing above, you can see this near the compressor where it is most evident. The F-15 has a low bypass ratio. It is also illustrated in this wikipedia graphic below–the bypass air is the arrow on the top left, a light purple color in the engine.

Compressor
Again, reference the Pratt & Whitney drawing above as well as the labeled wikipedia graphic. In the first, the compressor section (just in front of the orange section near the middle of the core part of the engine) is where turbine blades accelerate the air and increase the pressure, preparing it for combustion in the chamber just aft of the compressor.

This photo shows an excellent view the engine compartment along the full length of the bottom side of the F-15.
McDonnell Douglas F-15C/D Eagle

The inlet is also a critical part of the aircraft design because it ducts air to the engine. This photo of the lower part of the inlet also shows the engine compartment running the length of the underside of the Eagle.
McDonnell Douglas F-15C/D Eagle

McDonnell Douglas F-15C/D Eagle

The orange paint scheme, often referred to as a “clown jet,” is a distinctive characteristic of flight test operations.

Airplanes by Design features photographs of aircraft from a test pilot perspective, highlighting aeronautical engineering characteristics and flight test facts. To see all of the these pictures (and many more of this aircraft and it’s unique design characteristics), click here. You will always be able to access any of these pictures by selecting the Flickr icon in the top menu bar.

Click here to read more about this airplane.

Send a message to @FlightTestFact on Twitter to share your Airplanes by Design stories and photos.

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