Twisted ideas about warps
Dave Gee [email protected]
Last month, I discussed how vital a properly placed CG is to the safe and happy operation of a model aircraft. Close behind the CG in importance are the warps and alignment. Bent or cockeyed flying surfaces can make a model unsafe for flight. Have you ever seen a pilot struggling to keep a crooked RC model in the air? It’s too exciting for my taste!
Eyeballing a new model for straightness is the final safety check before it leaves the workbench. Instructions often suggest that the modeler “make sure there are no warps,” but this means no unwanted warps.
Any experienced modeler will tell you that not all warps are bad. Many airplanes need some washout (wing twist) to properly fly. This is a compromise between generating the most lift and getting the best stall characteristics.
Full-scale aircraft follow the same aerodynamic rules as our models. The Ronald Reagan Presidential Foundation and Library, located in Simi Valley, California, features a retired Air Force One. You will never see a more beautifully displayed aircraft!
A walkway brings visitors level with the wings and it is easy to see the washout that is built into the 707’s wing. That warp improves the jet’s flying characteristics, but you can bet that the designers measured it carefully! Our models need the same treatment.
CERT and disaster preparedness
What I wanted, and I don't only mean a spiffy, green hardhat.
The CERT Program educates people about disaster preparedness for hazards that may impact their area and trains them in basic disaster response skills, such as fire safety, light search and rescue, team organization, and disaster medical operations. Using the training learned in the classroom and during exercises, CERT members can assist others in their neighborhood or workplace following an event when professional responders are not immediately available to help.
The group provides excellent training and helps you think ahead so you'll feel less overwhelmed. The information might allow someone to be of great help to his or her neighbors and friends if things turn bad. The odds are that wherever you are, there is a CERT branch close by. If not, start one.
Full Speed Ahead
I don't know if Merritt Winner is involved in his local CERT chapter, but he is an experienced RC pilot, and he wrote to me about an upsetting incident with his model.
Merritt flies electric airplanes in the 12- to 17-pound range. He uses motor arming plugs, and has his transmitter programmed so the throttle stick is disabled until the transmitter switch enables the motor. He was cautious, as always, but did not expect discourteous treatment from his trusty 8-foot Telemaster.
"I treat every plane with a battery as if it were a loaded gun. If the plane has a prop on it, I also tie off the tail to the bench before connecting any battery," Merritt wrote. This paid off when he had trouble with a receiver.
"I was using a Futaba T9 CAP transmitter with a Futaba TM-8 FASST module on 2.4 GHz. The receiver has two modes. Normal is for analog servos at slower speed. The other mode requires digital servos (I don't have any) and results in twice the servo speed. It is shipped in the normal mode and I didn't change the mode setting.
"I had a momentary lapse of judgment and turned the transmitter off before I removed the batteries. The motor instantly went to full throttle! When I turned the transmitter back on, the motor stopped and all controls functioned normally.
"The speed-control programming requires switching the throttle stick to reverse so that off/idle is at the bottom and full throttle is at the top. I have checked my other planes, and all of them default to motor off when the signal is lost, even though they are programmed with the throttle stick reversed. I substituted a servo for the ESC and determined the R6008HS receiver defaults to the full-throttle position on loss of signal if the throttle stick function is set to REV.
"This seems like a real safety issue if the plane flies out of range or if the transmitter fails. I have many flights on this plane, with no control incidents. This situation was just waiting to bite."
There have been rare similar incidents with various makes and models of radio components. I'm no expert, but this could be a programming compatibility issue—some glitch in which the different pieces don't get along well. We may never know the cause of such trouble, but the lesson here is to be aware that it can happen.
Editor's note
As mentioned in the product manual, the R6008HS starts the linking process by pressing the Easy Link button for more than two seconds. When linking is complete, the R6008HS stores the throttle position as the F/S position automatically. If you need to change the F/S position, but don't need to relink, set the throttle stick as desired and press and hold the Easy Link button for 1 second. The receiver renews the F/S data for the current position. Before doing so, ensure that the F/S is active. If not, please follow the rearming procedure.
Check things and be prepared for sudden throttle changes as Merritt was. Although he was caught by surprise, his caution allowed this to be a close-call story and not a first-aid incident.
Sources
- Ronald Reagan Presidential Foundation and Library — (800) 410-8354 — www.reaganfoundation.org
- CERT — [email protected] — www.citizencorps.gov/cert/index.shtm
- Federal Emergency Management Agency — (800) 621-3362 — www.fema.gov
Transcribed from original scans by AI. Minor OCR errors may remain.
