Propulsion engineering and flight test truly covers the entire spectrum of flight test techniques. For example, consider these questions:

  1. Performance FTTs - Does the engine perform as expected?
  2. Flying qualities FTTs – Does a spin or stall or other high angle of attack disrupt airflow into engine inlets enough to cause engine flameout or compressor stall?
  3. Systems FTTs – Are the controls and displays associated with the engine adequate considering the mission of the aircraft? Does the Digital Engine Control interface appropriately with other aircraft systems?

Today, however, I would like to briefly describe throttle bodies, a flight test technique used, almost exclusively in propulsion engineering applications of flight test. (Bodies is pronounced with a long o, as you would expect to pronounce “bode–ee”.)

Initial setup: trim the aircraft hands off at a given airspeed and altitude and initial power setting.

This allows engine to stabilize. (Often the control room will look at telemetry from the engine to verify desired parameters are in range and stable.)

Maneuver technique: When command of execution is given, test pilot performs a step input to throttle. Test pilot observes engine response and in anticipation of the engine reaching desired setting, performs a second step input to original power setting.

This might be a rapid push of the throttle to maximum power or a throttle chop to idle, for example. The second input–a step input back to max for example–might be made as the engine passes 73% N1, so that the engine “bottoms out” at 65% N1.  In other words, this input must be made so that the engine does not pass the desired target parameters. Leading the desired parameter is required because engines do not spool up (or down) instantaneously.

Other considerations: Usually, the aircraft must maintain a constant speed (within some data band like +/-.05 M or +/- 5 knots). Thus at the initial trim condition, the pitch attitude might be nose high. When the throttle is chopped, the test pilot must pitch down to maintain the airspeed within the desired range. Similarly, this entire maneuver (including the pitch up/down) must remain within a certain altitude band (like +/- 1000 feet).

The illustration above from a Test Pilot School course handout (I encourage you to click on it to see it full size) shows the engine response to a throttle body.

On the last Friday of each month, the column What is an FTT describes some of the fundamental maneuver building blocks performed by test pilots to gather data during flight test missions. An FTT is in some sense a description of an experiment.  It is a key element of the scientific method applied to aerospace sciences, engineering, and aviation.

You can access all of these posts by clicking on the FTT category hyperlink below the post title.

#FTT Friday
Each Friday, @FlightTestFact will deliver examples, definitions, and explanations of flight test techniques for the entire day. You can view these tweets by searching for #FTT and #flighttest as depicted below. You can also click on the picture below to be taken to the twitter search results. What FTT would you like to know more about?


Read more: Previous | Next

An excellent, comprehensive resource for learning more about propulsion engineering is this Thermodynamics/Propulsion Engineering open courseware from MIT’s OCW project.

An extremely comprehensive listing of the specifications (thrust, specific fuel consumption, etc.) of jet engines is available from this website. When available, pictures and examples of each engine are provided.

 

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

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.

Click here to read more about this airplane.

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

The XB-70 was an experimental supersonic bomber that showcases an engine inlet designed to optimize supersonic airflow total pressure recovery with a changeable geometry.

NASA has several other XB-70 videos here.

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

Airplanes inspire and amaze us, especially as they dance through the skies accomplishing their stunning aerial feats. Nowhere is this more evident than in the unique videos that capture test flights by daring test pilots, pushing the very envelope of knowledge and ability. I think it makes people believe that with enough persistence, dreams do take flight.

I also believe that a video exponentially improves our ability to use picture to communicate 10,000 words, and this is not only one of the fundamental ATOMs but also an elementary and critical element in the strategy to inform and invest. These are just a few of the reasons that this weekly video column exists.

Wikipedia imageThere is a legend (and a delightful poem) about six blind men who examine an elephant.  The first finds the elephant’s side and declares that an elephant is like a wall. The second feels its tusk and compares it to a spear.  And so on and so forth it goes…with observations of its trunk, ears, tail and knee.

The end of the poem is as follows:

The disputants, I ween,
Rail on in utter ignorance
Of what each other mean,
And prate about an Elephant
Not one of them has seen!

Bad statistics is like the observations of blind men describing an elephant.

On the other hand, consider another blind man who had once seen an elephant in his childhood, or who, since he had become blind, heard stories from those who personally seen an elephant.  Armed with these descriptions, this blind man collects the same six pieces of data described above. Wouldn’t his observations make much more sense?

Good statistics starts with a question–it happens when you know, loosely speaking, what you are looking for, and you establish analytical methods for finding data that will help you answer the question you’ve asked.

Good statistics continues with an antithetical question–it considers what happens when you assume the opposite and examines the data in this light as well.

Good statistics is very powerful. It’s like a seesaw…but you’ll have to wait until next time to read about that.

This post is about a question I received on facebookCan a civilian airline pilot be a test pilot? The answer is definitely yes, and to adequately answer this question will take several posts. But here is the first part of my answer.

Test pilots need three broad areas of experience and expertise–aviation, engineering, and leadership–the airline industry has opportunities in each of these areas.

Aviation Experience
The airline industry is obviously a great place to build a strong foundation of aviation experience and flying hours. In fact, civilian airline pilots have a wide breadth of aircraft experience, from small general aviation aircraft to regional jets and perhaps even jumbo jets. Learn as much as you can about the airplane you are flying. Read the aircraft operations manual frequently. When you get the opportunity, talk to maintenance personnel and learn more about the airplane that way as well.

Leadership Experience
Even as a junior airline pilot, as a first officer, you should and can begin to grow as a leader. Watch what the experienced captains do and say as the pilot in command, how they act, and take every opportunity to ask them about their experience. Everything you learn about leadership will help you grow in your aviation career–you will need many strong leadership skills to excel in flight test.

Engineering Experience
Every airline has a collection of pilots who have a strong background in technical skills and a deep understanding of the maintenance aspects of the aircraft. Some airlines have test pilots on their staff. Almost every maintenance facility has pilots who fly the aircraft in a functional check flight (or acceptance test flight) after maintenance is done to ensure that the aircraft and its systems still function properly. This is the tip of iceberg for the kind of skills you will need as a pilot-engineer, which is one of the hats that a test pilot wears. These pilots are the bridge between the engineers/technical experts and the pilots who fly the line every day.

I recommend that you find these pilots and offer to buy them coffee or lunch in exchange for an hour of questions and answers. What you learn about their career path may be exactly what you need to launch your flight test career.

Next time, I’ll offer some suggestions on courses you can take anywhere in the world regardless of your engineering background or citizenship to begin to equip you with some fundamental flight test knowledge.

Don’t just imagine your dreams–explore them, because we need you. The aerospace industry needs innovators. The flight test community is looking for the next Neil Armstrong, and that’s what this column is about, helping you take that next small step. 

Thanks for reading Launch Your Flight Test Career #2Send a message to @FlightTestFact on Twitter to ask questions about launching your flight test career.

More articles in this series: Previous | Next

Two of the world’s leading jet engine manufacturer’s have wonderful multimedia presentations and references on jet engine operation and on the particular characteristics of their products.

General Electric’s Engine 101

Pratt and Whitney discuss their engines, like the C-17A’s F117 engine here.

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

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.

Early development of vertical takeoff and landing aircraft centered primarily on propulsion engineering and it’s use in providing lift and stability/control and thrust as seen in this documentary video.

(Thanks to flightglobal.com @flightblogger for the lead on this video.)

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

Airplanes inspire and amaze us, especially as they dance through the skies accomplishing their stunning aerial feats. Nowhere is this more evident than in the unique videos that capture test flights by daring test pilots, pushing the very envelope of knowledge and ability. I think it makes people believe that with enough persistence, dreams do take flight.

I also believe that a video exponentially improves our ability to use picture to communicate 10,000 words, and this is not only one of the fundamental ATOMs but also an elementary and critical element in the strategy to inform and invest. These are just a few of the reasons that this weekly video column exists.

What does it mean to transform uncertainty?

I think this is an important question for at least 4 reasons:

  1. We are drowning in data.
  2. It has come into the focus of  mainstream media (like this Forbes article).
  3. It is a fundamental element of the mission of mc2, and
  4. “Transforming” is a fundamental illustration and analogy in the branding of this company and website.

So what does it mean?

Transform
To begin with, Zig Ziglar does an excellent job explaining what it means to “transform” in his book, See You at the Top.*

Take a bar of iron and use it for a door stop and it’s worth a dollar. Manufacture horseshoes from that iron and they’re worth about fifty dollars. Take the same bar of iron, remove the impurities, refine it into fine steel, manufacture it into mainsprings for precision watches and it’s worth a quarter of a million dollars.

The way you see the bar or iron makes the difference…

I think the way you see data, especially in aviation and aerospace and flight test, makes the difference.

Uncertainty
You might see uncertainty and noise and risk. You might see a deluge of information, like a wall of rain falling from the sky, making it difficult to see.

Or, if you are equipped with some fundamental analytical tools, you might see that flipping a coin results in a fair decision rule that a referee can use to decide who kicks off first. You might see that the idea transforming data has amazing potential, the kind of nearly unlimited energy available from transforming the natural flow of water into hydroelectric power, just by building a dam.

Still wondering how “transforming” illustrates the branding of this company and website?

This picture is a hint…what happens when you transform matter into energy? There’s an equation for that.

I have been extremely privileged to meet and be mentored by test pilots and flight test engineers from all over the world, from every background and career path. I’ve summarized the well-traveled of these paths below.

Here are nine ways to get your flight test career off the ground:

1. Military Test Pilot School – like USAFTPS or USNTPS
2. Civilian Test Pilot School – like National TPS (NTPS)
3. Production flight test (described in an Air & Space Magazine story here)
4. FAA Flight Test (both engineers and pilots are needed to support FAA’s certification responsibilities)
5. Maintenance test flights
6. Airline technical/engineering pilot
7. Study at a college with a flight research/flight test laboratory (MS State, Texas A&M, UTSI, etc.)
8. Build and fly your own aircraft
9. Flight test of unmanned aircraft

In the weeks ahead, I will share stories from my friends and colleagues in each of the above categories, so you can see how they found their dream job in the flight test/aerospace industry.

Don’t just imagine your dreams–explore them, because we need you. The aerospace industry needs innovators. The flight test community is looking for the next Neil Armstrong, and that’s what this column is about, helping you take that next small step. 

Thanks for reading Launch Your Flight Test Career #1Send a message to @FlightTestFact on Twitter to ask questions about launching your flight test career.

More articles in this series: Previous | Next

With elementary line drawings/illlustrations like this one, the Test Pilot School’s introductory handbook on propulsion flight test is an excellent choice for beginner or a quick reference for the expert.

Introduction to Propulsion Engineering and Flight Test Handbook (USAF TPS)

It includes discussion on computing engine efficiencies, inlet design, thrust and specific fuel consumption derivations, etc.

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

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.

The Top Gun “flat spin flameout” is not that far-fetched. Airflow during high angle of attack maneuvering can have a significant (and sometimes detrimental) effect on aircraft engines. Therefore, spin-type flight testing is a key part of propulsion engineering analysis. The following videos show spin testing of the F-15.

The next video includes cockpit footage as well.

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

Airplanes inspire and amaze us, especially as they dance through the skies accomplishing their stunning aerial feats. Nowhere is this more evident than in the unique videos that capture test flights by daring test pilots, pushing the very envelope of knowledge and ability. I think it makes people believe that with enough persistence, dreams do take flight.

I also believe that a video exponentially improves our ability to use picture to communicate 10,000 words, and this is not only one of the fundamental ATOMs but also an elementary and critical element in the strategy to inform and invest. These are just a few of the reasons that this weekly video column exists.

Every time I hear the word “self-employed” or “solopreneur” (a solo entrepreneur), it makes me want to vomit. Let me explain why…

It was January of 2002, and I was stationed at Moody Air Force Base (AFB), living by myself in Valdosta, Georgia, because Beth was finishing college in Hawaii. We had been together at Christmas as a family, but vacation was over. Pilot training was back in full swing.

Air Force pilot training is hard, even if everything goes right. (I was reminded of this many times in the past eight months, as I re-qualified in the T-6 at Randolph AFB from July-November, and then completed the local area orientation check-out at Columbus AFB, a pilot training base in Mississippi.) But I knew that pilot training was a step in the direction of my dreams to become a test pilot.

That January, things started to go sour. The first time I flew a loop, the airplane went one way, and my stomach went the other. The second time, the airplane went one way, and my lunch went another! Airsickness–at this particular stage of the program–was a major problem. I was on the verge of washing out, perilously close to failing pilot training.

The Air Force has an extensive torture program designed just for this kind of situation, and its code name is the Barany Chair.

Spinning in Circles
I cannot even begin to describe the experience. You can see this device in the picture here, but I assure you, the team that follows real Barany Chair protocol does not smile like these airmen are.

For ten minutes at a time, the aerospace physiologist would spin me around, having me move my head this way and that–stimuli to aggravate the inner ear and induce motion sickness.  They build up the stimuli–the first time, you just feel a little bit sick, and then they reduce it. The second time, it’s a little bit sicker.  After that ten minutes is up, there is a ten minute rest followed by two more cycles like this. Most times, the protocol ended with the must gut wrenching vomiting…on the good days.

On the bad days, the days I didn’t void my stomach, I felt even worse. I don’t know why, but a recently vacated stomach left…nothing left to be upset about…and actually felt better. The protocol was horrific. I hated it. Despair is the only word I can use to describe that situation.

Every night that week, I would call Beth: “I just want to quit. Pilot training isn’t worth this.” She voiced encouragement. (This wasn’t the first time, and it hasn’t been the last time.)

Walking in Circles
German scientists demonstrated that people who are lost end up walking in circles. Furthermore there seemed to be no systematic bias evident–variation occurred in both directions. This happened when outside sensory cues were absent or diminished. When the sun was out, the “lost” had something with which to guide their way.

It’s hard to imagine walking in circles by accident–it’s hard to imagine getting lost. We live in a world of interstate highways and sidewalks and “you are here” signs. For those of us who venture out into nature, it’s usually on a trail system or loop. As long as we stay on the path, we won’t get lost.

Exploring uncharted territory doesn’t come naturally in today’s day and age. In Poke the Box author Seth Godin says, “Human nature is to need a map.” It’s also human nature to need a GPS in our cars, on our bikes, and in our phones.

What if I lose sight of the sun?
If your dream is big enough, it takes you into uncharted territory, off of the sidewalks and highways.

Sometimes, I lose sight of the sun. It’s easy to lose sight of the sun when you are spinning in circles on a Barany chair or staring at the bottom of a barf bag. I didn’t need to see it, though–Beth was still looking up. She could see the sun.

So every time I hear the word “self-employment” or “solopreneur,” it reminds me of a time and place…that I don’t want to revisit. I can almost taste the bile in my mouth.  Any journey of value wasn’t meant to be travelled alone.

What I’m saying is, we need someone–I’ve got Beth–to help us see the way the Son is leading us. That’s three people–at a minimum–in this thing that I personally don’t want to call “self-employment.”

You’ve just read confessions of a freelance test pilot, a monthly column that illustrates in my personal life and leadership the technical concepts found in ATOMs. Some people may not want the technical content that appears on this website–if you only want to follow these more personal updates, I set up a special subscription for that option here: by Email or RSS.

NASA Photo: F-15 Propulsion Flight Test FixtureAs the propulsion engineering sub-discipline and aircraft engine characteristics are the focus of this month, here are several excellent references on flight test and engineering design of engines.

Propulsion is covered specifically in chapter 24 of the AGARD Flight Test Technique series, Volume 14. The full text of this volume is here

Unique methods of propulsion flight test include NASA’s Propulsion Flight Test Fixture (pictured above), and this report discusses its initial flight tests.

AGARD Advisory Report No. 81 TECHNICAL EVALUATION REPORT ON FLUID DYNAMICS PANEL SYMPOSIUM ON AIRFRAME/PROPULSION INTERFERENCE

This month continues the column feature begun in January with the ABCs of aircraft engines.  Aircraft engines are highly complex, and thus, the characteristics manifest themselves in many ways around/in an aircraft.  The photos that appear below begin to suggest just how varied engine photos can be, by comparing 5 kinds of aircraft engines from a variety of perspectives. (Of course, these are not in alphabetical order, but I had to start somewhere.)

Propeller
Carbon Cub forward view looking aft, engine, propeller, inlet, cowling, main landing gear

The Carbon Cub has a traditional, fixed-pitch prop run by a simple, piston-driven combustion engine.

Turboprop
Raytheon Beechcraft T-6 Texan II

The T-6A Texan II is my favorite turboprop. The PT-6 turbine engine that drives the variable pitch, constant speed prop is unusual in two ways: 1) air enters at the back of the engine and travels forward, and 2) the compressor section and turbine section of the engine are not connected/do not share the same shaft.

Scramjet
X-51A Waverider

A scramjet is a jet engine that uses the dynamic pressure of the air to compress it enough for combustion. It is also the supersonic version of a ramjet. This is the X-51 Waverider experimental aircraft.

Turbojet
NF-4C Phantom II
The difference between a turbojet and turbofan is subtle and nearly impossible to see without peering “inside” the engine, but nevertheless, the F-4 is a classic airplane and excellent example of the turbojet, originally designed with the J79. This photo reveals the afterburner section of this engine, another variable in the design of turbine engines. My father was an F-4 weapons system officer, so it probably has a special place in my heart among turbojet aircraft.

Turbofan
C-17A Right wing forward view looking aft

This is a picture of the number three engine on my favorite turbofan powered aircraft. Next week, we will examine “bypass ratio” in the first alphabetical look at engine characteristics.

Of course, all of these examples might make you wonder why someone would design an aircraft with one particular engine rather than another. Complexity, cost and function are all variables. For example, propeller engines are more effective in the sense that they have more specific excess power at low airspeeds, as seen in this chart.
Typical Excess Power Characteristics Prop vs Jet screenshot

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.

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

This video shows air-to-air photography/videography taken by a chase plane during a practice Flight Test Technique (FTT) performed at the USAF Test Pilot School. The purpose of the FTT is to observe and evaluate the afterburner light-off process, a type of propulsion flight test.

Notice that the F-16 begins the maneuver with the speedbrake extended. This is to prevent rapid acceleration away from the camera as the afterburner ignites.

Check out @FlightTestFact on Twitter for more flight test safety references, videos, and information daily.

Airplanes inspire and amaze us, especially as they dance through the skies accomplishing their stunning aerial feats. Nowhere is this more evident than in the unique videos that capture test flights by daring test pilots, pushing the very envelope of knowledge and ability. I think it makes people believe that with enough persistence, dreams do take flight.

I also believe that a video exponentially improves our ability to use picture to communicate 10,000 words, and this is not only one of the fundamental ATOMs but also an elementary and critical element in the strategy to inform and invest. These are just a few of the reasons that this weekly video column exists.

It was a month of new beginnings. Several familiar columns started new segment features, and several new columns were added.

Confessions of a Freelance Test Pilot
What is it like to run on a new trail? It’s analogous to exploring new scientific theories or a new part of the aircraft envelope. Click here if you want to start back at the beginning of the confessions category.

Flight Test Videos and References
Catch up on last year’s most popular videos and some new ones–F-16 departure or space shuttle approach/landing flight test  that illustrate some unique flight test characteristics in this category.

Airplanes by Design
This month kicked off a new segment in the Airplanes by Design category, where we examine aircraft design characteristics alphabetically. January was the ABCs of aircraft wings, and similarly, February will be the ABCs of aircraft engines.

ATOMs
Analytical tools of mathematics and statistics (ATOMs) are fundamental to the purpose of this blog, and this month recounts a harrowing anecdote that illustrates the importance of these principles.

You Can Be a Test Pilot
A new column monthly answers questions about what it takes to launch your flight test career.

Flight Test Technique – #FTT Friday
The first #FTT Friday monthly post answered the question “What is an FTT?” and features Friday tweets from @FlightTestFact.

 

 

Monthly Review: Next

A flight test technique (FTT) is a tool for answering common or frequently asked questions in flight test. It is a maneuver building block consisting of procedures for accomplishing the maneuver together with an objective and metrics.

FTTs are the “questions” that we ask to investigate various characteristics of airplanes.

For example, we may wish to know about the stall characteristics of an airplane. Since aircraft stall is a complex and non-linear phenomenon, one that is not well-understood, we must approach this boundary in the flight envelope in a very methodical, incremental, intentional, and safe way.

Pictured here is a portion of the test card used for gathering data about the stall characteristics of an airplane.

A FTT is in some sense a description of an experiment.  It is a key element of the scientific method applied to aerospace sciences, engineering, and aviation.

There is a growing index of FTTs available here–if you are looking for something specific, please let me know, and I will address it.

#FTT Friday
Each Friday, @FlightTestFact will deliver examples, definitions, and explanations of flight test techniques for the entire day. You can view these tweets by searching for #FTT and #flighttest as depicted below. You can also click on the picture below to be taken to the twitter search results.