Jet/Long Ranger/206
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Rotorcraft; Flight Crew Flight Instructor
Flight Crew Last 90 Days 234; Flight Crew Total 10160; Flight Crew Type 2876
Troubleshooting; Human-Machine Interface; Confusion; Communication Breakdown
Aircraft Equipment Problem Less Severe; Airspace Violation All Types; Deviation / Discrepancy - Procedural FAR; Flight Deck / Cabin / Aircraft Event Other / Unknown
Flight Crew Overcame Equipment Problem; General Maintenance Action
Human Factors; Aircraft
My KT70 Transponder squawked 1200 uncommanded inside a Special Flight Rules Area (SFRA). I was in cruise flight and had no part of my body near the push [button] for 1200 post. This is the third KT70; all with different serial numbers; to squawk 1200 uncommanded in a Bell 206L4 Helicopter. It seems there is an airframe or installation issue with this aircraft. My company has been slow to understand the seriousness of this issue and does not want to seek the real cause of this problem. I will be the second pilot flying this Bell 206L4 being investigated for possible violation due to this strange electromechanical defect. Flying from a Base of operation far removed from headquarters; while flying special airspace; is challenging. Even before the equipment failures; I warned against using this model transponder with a push button to squawk 1200. I was ignored repeatedly and dismissed with some scorn. After this third transponder failure my company is now doing what I asked for five years ago.Avionics specialists say the KT70 cannot squawk 1200 uncommanded; that is not true. In this aircraft; a KT70 Transponder has failed about once every 2 months since July 2015. This Helicopter is equipped as an Electronic News Gathering (ENG/News) helicopter; I believe the ENG installation is the cause of the transponder failures. There is a lot of stray electromagnetic energy from power supplies; transmitters; and camera motors. It interferes with my radios and in extreme cases may trip the KT70 to squawk 1200. We are installing an old transponder without the 1200 squawk button. We will never know what the problem was. This was an upsetting event that distracted me from my duties as PIC near the traffic pattern of the local airport. Is the persecution and harsh treatment for squawking 1200 by accident or mechanical failure worth it? What does it accomplish?
The Reporter stated that in the KT70 Transponder (Tx) mounting rack; there is an Interface circuit board that mates with the Transponder when it's installed. That circuit board is separate from the Transponder and is attached to the mounting shelf; not the Transponder. After further; persistent investigation; an Avionics Maintenance Technician (AMT); discovered that the Interface circuit board; which has a female receptacle; was not securely attached to the rack and did not make proper contact when the male end of the Transponder was installed in the rack. That loose connection and normal vibration from the helicopter was believed to have caused conflicting signals in the KT70 Transponder that resulted in the Transponder defaulting to an uncommanded initiation of the 1200 squawk code. Reporter stated that to temporarily resolve this issue; an older KT76 Model Transponder was installed that did not have a 'push button' for squawking 1200.
A Bell 206 Helicopter Pilot reports the aircraft's KT70 Transponder squawked 1200 uncommanded; while he was flying in a Special Flight Rules Area (SFRA). His event was the third incident of an uncommanded 1200 squawk that occurred in the same Bell 206; even after three KT70 transponder replacements. After persistent troubleshooting; an Avionics Maintenance Technician (AMT) found a loose Interface circuit board.