Counterfeit Futaba Servos

Counterfeit Futaba servos exist. My students and I managed to purchase a few for a recent aircraft project. These were purchased off of Amazon. We now call these “Faketaba” servos.

Question: How many ways can you tell that the following servo is a counterfeit Futaba S3003 servo?

IMG_2579

Answer:

  • The servo performance is significantly worse than a genuine servo. In fact, I (Charles O’Neill) initially discovered that these servos were not genuine after performing a systems check of installed servos. The return to zero had a hysteresis of about several millimeters at the servo horn, which gave a surface deflection static hysteresis “zero” of about +-10 degrees. This was completely unacceptable for our application. These were immediately removed and replaced.
  • The Futaba logo and font is not correct. As a typography enthusiast, I spotted the slight imperfections in the name sticker.
  • Gear noise is sigificantly higher for these fake servos. The gear geometry and tooth count are different from actual Futaba servos. IMG_2581
  • In addition to the gear noise, the output shaft tolerance created an issue with the bearing surfaces. Also, the spline shaft poorly fit the servo horns. The servo horns themselves were significantly thicker than genuine horns.
  • After installation, I went back and found the box that the servos were shipped in. This is obviously not a genuine Futaba box.IMG_2577IMG_2578
  • I opened one servo to investigate the counterfeit quality. The grommet was not sealed correctly, a mistake that the Japanese Futaba company would never allow. The motor is only press fit into the servo case; this is a sneaky possible failure point. The servo case is geometrically different from an actual case.

IMG_2580

  • The mounting holes are opened at the end. Actual Futaba S3003 servos are closed.

One additional point of discussion, the cost for these counterfeits was similar to actual genuine servos. My students learned a difficult lesson in trust.

Students’ Websites

My students are strongly encouraged to demonstrate their capability through a web presence.

 

Flight team at the University of Alabama.

This is an informal group of UAV and RC aircraft pilots and designers who meet each Friday at 4pm to fly and learn to evaluate aircraft.

The group is also provides UAS training for FAA certification within Part 107. Contact croneill@eng.ua.edu for details.

IMG_2352

Lockheed A-12 Logging

This page exists to log my visits to the surviving Lockheed A-12 aircraft. Photos are in serial number order.

A12 60-6933

A12 60-6933 at the San Diego Air & Space Museum

 

A12 6937

A12 60-6937 in Birmingham AL

60-6925 in NYC: no photo

 

 

GPS WAAS Update (Magellan Sportrak)

Today, we manipulate bits to resurrect a hobbled 15 year old GPS receiver. In the process, I learned about WAAS and s-records to successfully update a client’s  Magellan Sportrak GPS unit.

calc

waas_sats

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Hinge Moments Thesis Defense (C. Simpson, MS)

Today, my MS student Mr. Christopher Simpson successfully defended his thesis:

CONTROL SURFACE HINGE MOMENT PREDICTION
USING COMPUTATIONAL FLUID
DYNAMICS

The work demonstrated several key concepts necessary for the use of CFD in rapid aircraft prototyping of aircraft control surfaces. The thesis evaluated both 2D and 3D geometries using NASA LaRC’s FUN3D computational fluid dynamics software.

GAW1 d20

Christopher also conducted unsteady and adjoint refined solutions.

Unsteady Hinge Moments

This page will be updated when his final version is submitted.

Southern Museum of Flight tour for Aircraft Systems

University of Alabama AEM 617 students visit the Southern Musuem of Flight's A-12

University of Alabama AEM 617 students visit the Southern Musuem of Flight’s A-12

Today, we get a behind the scenes visit of the Southern Museum of Flight in Birmingham, AL to discover the complexity of aircraft systems. In the process, my class of graduate students learn to see aircraft in a different light.

Special thanks to the museum director Dr. Brian Barsanti. My students received a rare treat, a guided tour with both a professor of history and a professor of aerospace engineering.

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Mars Atmospheric Reentry Profiles

Landing on Mars is a difficult engineering problem. A recent conceptual project demonstrated this reality through the atmospheric reentry profile. In other words, assuming that your spacecraft approaches Mars at 200 kilometers and 6.5 kilometers per seconds, what is the altitude-velocity profile during the reentry trip?

Complicating the situation is an observation that your vehicle’s aerodynamics strongly affect the profile. In particular, increasing the life decreases the observed g-load, but leads to atmospheric skip when the lift is not controlled.

Reentry

A ballistic reentry vehicle should expect a maximum g-load above 10 in the 50 km altitude region. This conceptual analysis strongly suggests that manned reentry to Mars will require hypersonic aerodynamics generation of a lift over drag (L/D) ratio in the 0.5 range.

Wing and Airfoil Theory class (AEM 614)

The graduate level AEM 614 Wing and Airfoil Theory class at the University of Alabama was resurrected, developed, and taught in the fall of 2015.

The course used two textbooks:

Flight Vehicle Aerodynamics, Mark Drela, MIT Press, 2014
Aerodynamic Design of Transport Aircraft, Ed Obert, IOS Press, 2009

Student Evaluations: 15Charles O’Neill (AEM 614-001 Airfoil And Wing Theory)

Discrete Vortex Panel Solver

Aerospace engineers encounter vortex methods as undergraduates. The famous thin airfoil theory is a continuous vortex sheet. The famous XFOIL is a panel method with an IBL solver for viscous effects.

Q: Can a simple discrete vortex method capture thickness?

A: Yes, but I would recommend a linear vortex method instead.

naca4412a10

NACA 4412 at 10 degrees: 200 Elements

naca4412a10coarse

NACA 4412 at 10 degrees: 16 Elements

The source code and executable are available here.

The visualization is a pure Fortran library exporting to scalable vector graphics (.svg).