This new column will feature a brief description, photo or video, and/or reference that talks about a Flight Test Technique that students at USAF Test Pilot School are currently learning. It’s an alphabetical list of FTTs together with a chronological account of what future test pilots and flight test engineers are doing right now. It will complement the previous Friday’s FTT tweets as well.
What is a doublet?
1. An elementary open loop maneuever performed in a single axis of motion.
2. A flight control input used in flying qualities flight test to excite an aircraft mode of motion. Here is a video of a Bonanza doing a rudder doublet to excite the lateral directional modes of motion.
3. A symmetric input in both directions–for example, you could push the stick forward one inch then pull the stick back (past neutral) one inch and then return to center.
Here is a time history plot of the response to a doublet performed using rudder pedals, for example.
Source: sciencedirect.com via Flight on Pinterest
What is a singlet?
An asymmetric flight control input in one direction. For example, you could push the stick forward one inch then then return to center.
Here is a time history plot of the singlet – the flight control input (elevator) is the third line, and the other lines are the aircraft response.
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This post summarizes references and #FTT tweets from the previous Friday. What is #FTT Friday?
#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?
For more information, you can read the post What is an FTT? or check out the alphabetical index or the FTT blog category for several examples, test cards, and videos of FTTs.
