Another visit to my favorite Greece

sounio_flyby

Short vacations back to homeland. From perfect jumps, to snorkeling, flights, and meeting friends and relatives.
I get so many comments about the economical state and the crisis in my country lately. Huge political errors made in the last 4 decades have resulted in this unfortunate situation, but … I remain optimistic. The errors will eventually be paid by various forms of pain, and Greece will stand strong in its own feet again. I just hope it does not take too long.

After all, υπεράνω όλων η Ελλάς..

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Drag polar determination paper to be presented in Annual SFTE Symposium, Lancaster, CA

A THEORETICAL REVIEW OF THE EFMA FLIGHT TEST TECHNIQUE AND EVALUATION METHOD

Abstract

The Excess Force Mass Acceleration (EFMA) Flight Test Technique and Evaluation Method calculates the drag polar and the propulsive tangential force for an aircraft without requiring any engine thrust information or extensive instrumentation. The EFMA method was initially developed and evaluated in a collaborative effort between USAF TPS, German WTD61 and EADS Germany in 2001, however very limited documentation was available on the method in the flight test community. The present paper revisits the EFMA method providing a deeper insight in the theory behind it and re-derives the describing equations using minimum approximations. The method’s individual steps are finally presented in a form convenient for application.

efma_fig

Fig: Aerodynamic and propulsive forces during a dynamic manoeuvre.

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UAV Flying Qualities… what do you really mean?

It has been observed that in the flight test and operational communities the definition of UAV flying qualities (FQ) has not been clear to everyone. A 2003 paper titled “UAV handling qualities… you must be joking” is just an example of the confusion that can arise when extrapolating the standard meaning of manned vehicle FQ to unmanned. The many differences encountered between manned vehicles and unmanned vehicles/systems are inevitably translated to a difference of how FQ are perceived for each case.

UAV_fq

One of the the first guidance on UAV FQ as given by TECHNICAL REPORT AFFDL-TR-76-125 [1] was the following:

“In studying RPV flying qualities, the total RPV system must be considered. This includes not only vehicle stability and control, but must also encompass automatic and manual control, command and data link, and the man-machine interfaces (i.e., display information and controls) which directly affect the flying qualities of the RPV.”

Since 1976 that the text above was written, the UAVs have been strongly coupled to advanced payloads and autonomous flight, which should be included in a way or another in the flying qualities definition (notice that in the guidance above, though reference is made to a system where many different parts influence FQ, there is no mention to the carried payload). A more recent definition of UAV FQ goes a bit further including the onboard payload/sensor as part of the evaluated system. Two excellent references on the subject are from Dr M. Christopher Cotting, current FQ head lecturer at USAF TPS [2,3].

For the case of manned air vehicles, one of the several definitions that Cooper and Harper make is that of declaring Handling Qualities and Flying Qualities as synonymous with the definition of:

“those qualities or characteristics of an aircraft that govern the ease and precision with which a pilot is able to perform the tasks required in support of an aircraft role.”

This definition can be altered for use by UAVs by defining UAV Flying Qualities as:

“those qualities or characteristics of an aircraft and sensor system that govern the ease and precision with which an operator is able to perform the tasks required in support of its mission role.

As the later definition goes further than just the flying part, it seems that UAV flying qualities have a meaning closer to “mission qualities” which considers the payload and can be also applicable for autonomous flight.

GA_new_cockpit

Towards this “vehicle-payload system” direction, a UAV Performance Rating Scale has been proposed based on the Cooper–Harper piloted rating scale [3]. While the scale looks very similar to the C-H scale, a closer look reveals a number of significant differences. Any interested reader is strongly suggested to study the describing paper and explore through application the strengths and weaknesses of this proposed UAV scale.

[1] C. F. Prosser, and C. D. Wiler, RPV Flying Qualities Design Criteria, AFFDL_TR-76-125, December 1976.

[2] M. C. Cotting, Evolution of Flying Qualities Analysis: Problems for a New Generation of Aircraft, PhD Dissertation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 2010.

[3] M. C. Cotting, UAV Performance Rating Scale Based on the Cooper-Harper Piloted Rating Scale, 49th AIAA Aerospace Sciences Meeting, 4 – 7 January 2011, Orlando, Florida.

PS: Blog post published in the island of Lefkada, Greece.

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3 years of aeroscience… Hola!

The third birthday of aeroscience blog finds it somewhere in Cuba, celebrating with the company of a Cuba libre and Guantanamera rhythm.
A probably expected conclusion of this trip is that people differ across the world, cultures differ, music, languages and religions differ, scenery differs, but what remains exactly the same are the consequences of communism.

cuban_car

PS1: I spent in Cuba 7 days. During my flight back I found myself thinking on political systems. I strongly believe that the effect of communism on the vector of human evolution is to revert its direction. Theoretically, if communism could be applied long enough homo sapiens will eventually become a fish. Fortunately this will never happen as apes would never adopt this political system. 

PS2: Significant part of my mind is back in my country and the difficult times it goes through. 

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F-5 Supersonic Flight

supersonic_self

A qualitative evaluation and supersonic flight in a NF-5B flight took place in KJAX Florida. A unique feeling and experience flying in the front seat of this maneuverable fighter. Maximum Mach number reached 1.1 at 26,000ft while significant part of the flight was performed in the transonic and high subsonic region. Great lessons learnt in the challenges presented in flight testing this category of airplanes and this speed range. The only problem is that now that I have tried it, I want more…

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Tribute to a friend

Jesuardo_

I met Jesuardo at Forth-Worth TX in 2013. He approached me and asked me “Are you the author of aeroscience blog?”. I replied positively. “That’s great, I follow it!” he said.

From that point and throughout that Symposium we spent significant time together, he was very friendly, kindhearted and enthusiastic guy with great respect for everyone, making nice jokes and keeping always a smile on his face. I felt that we were friends from before. I met also his wife, Jesuardo seemed to really enjoy the time he spent with her. By the end of the symposium we greeted each other and made an appointment for the next year. Unfortunately in the Symposia that followed his colleagues always informed me that he was busy and could not attend, till the NATO Symposium in Ottawa. He was a member of the organizing committee, he had to attend. I couldn’t wait to meet him again!

The first morning of the NATO Symposium I went directly to his colleagues asking where I could find him. Their reply came as a shock: “Jesuardo was killed in the A400M crash, last Saturday”….

… It took me few days to comprehend his loss. My thought continually circled around him, his wife and the two children that he left behind, reminding me in the harshest way that flight test can kill…

Fare well my dear friend. We ‘ll meet again…

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Flying the Wright Flyer B

Unique experience flying in the replica of Wright Brothers second airplane. Literally open cockpit flight with unconventional controls, makes you built enormous respect for those pioneers and their incredible machines!

WrightFlyerB

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