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Every engineer has their own opinion about aircraft design, but there are three important characteristics of an airplane that the end user cares about: 1) Performance, 2) Flying Qualities, and 3) Systems. What makes airplane design difficult is that you cannot change one without changing the others. I’ll illustrate with pictures of the F-35 JSF.

 

Performance
Performance answers questions like: How high, and how fast? For example, how fast can the F-35 accelerate from 0.8M to 1.2M, the critical transonic region? A glance at it’s underside reveals a large cross-section, a weakness that mother nature exploits with wave drag. Initial design called for longer and more slender, but it was too tail heavy.

 

Systems
Systems allow the pilot to use the airplane to get it’s job done. In the case of the F-35, that’s to fly and fight. You can see part of the DAS (distributed aperture system), a collection of sensors, that appears as a bump under the nose of the aircraft below. Systems are needed to get the job done but add drag and take up valuable real estate inside the airplane.

 

Flying Qualities
Understanding how the airplane responds to mother nature’s laws will reveal how it responds when pilots ask it to turn tighter while looking over the shoulder in a dogfight. That’s the objective of flying qualities testing like high alpha and spin testing, as shown here. Pilots want the airplane to be responsive and maneuverable, but that can make it unexpectedly hard to fly in places like high angles of attack.

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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. 

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#Aeroindia starts today — here’s a very brief intro at the flight test sliver of the amazing aerospace industry thriving in India. Check out the aeroindia website too.

This week’s photos take another look at aircraft from the perspective of various engineers introduced last time.

HAL Tejas
The Hindustan Aeronautics Limited (HAL) Tejas is the primary fast jet trainer aircraft at the Aircraft Systems and Testing Establishment, home of the Indian Air Force Test Pilot School.

Aerodynamicists will immediately notice the absence of a horizontal tail surface.

Top view HAL Tejas
A top view of the aircraft reveals a unique delta wing design with two sweep angles. Inlets below the wing will attract the attention of the propulsion engineers. And systems/avionics types will notice many antennae for sensors.

The test pilot school is largely supported by HAL, India’s leading aerospace R&D organization.

To read more about the Indian Air Force check out these links:
1. Interview with an Indian Test Pilot about TPS

2. Overview of the Aircraft Systems and Testing Establishment (ASTE)

3. Wikipedia article

Empire Test Pilot School (ETPS) is the UK’s test pilot school located at Boscombe Downs, UK.  On final approach to their primary runway, one passes the ancient wonder Stonehenge, which is quite a treat.

I was able to visit ETPS as a student at the USAF TPS.  While there, I flew their ASTRA Hawk, an Alpha Jet, and a Tornado, one of the few remaining variable sweep wing aircraft.  Unfortunately, two of these aircraft are no longer presented on the ETPS website.

The ASTRA Hawk

 

The Hawk aircraft at ETPS is a variable stability simulator, with an onboard computer that allows it to emulate the flying qualities of almost anything, including many other aircraft. This picture reveals the aircraft’s tail anhedral and some aerodynamic bandaids like a wing fence.

The Saab Gripen

Another primary curriculum aircraft is the Saab Gripen.

QinetiQ also operates a high fidelity simulator as part of the curriculum for R&D.

 

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Airplanes by Design features photographs of aircraft from a test pilot perspective, highlighting aeronautical engineering characteristics and flight test facts. You will always be able to access any of these pictures by selecting the Flickr or Pinterest icon in the top menu bar.

WANTED: Your pictures and videos.

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