14 April 2022

The Recalcitrant Transponder

It was 9 March, with two rigs to fly to.  The first was to Malikai, not even 30 minutes from Kota Kinabalu. It was still only a fortnight since my promotion, and just my third offshore sortie with a copilot into whose hands I was going to trust my life whenever the approach to a helideck favoured the left hand seat pilot. This does require some acclimatisation. At time of writing, I am comfortable with the concept. It took me a very short time because the manning levels here in KK present me with only 4 copilots whose judgement I would have to yield to.

The winds were still north easterly. Malikai was the copilot's landing with the prevailing wind from the north east. It looked like it was going to be a predictably routine day. Since there were only two sorties, or sectors, we continued at an unhurried pace about our business with refuelling and the pre flight paperwork for the second sortie to Maersk Viking, the new kid on the block adjacent to Gumusut Kakap. 

This was to be the captain's landing, therefore the take off and outbound flight fell to me. All went well till upwind after initial take off and KK Tower handed us over the Kinabalu Radar. After the initial check in with Radar, the controller seemed unusually quiet, while paying attention to the other traffic under her purview. I prompted the copilot ( I'm making an effort to use third-person references in the interest of privacy) to request direct track to the destination from her. The controller then came back saying "WS, you are not radar identified. Turn left heading 2-9er-0 for Maersk Viking."

OK, I noted. Our transponder doesn't seem to be readable by Air Traffic Control. I checked the Control Display Unit and saw that the the Transmit cursor was blinking happily, indicating that the transponder was indeed, transmitting. Depressing the Ident button on the line select keys, I called in to the Radar Controller and declared I was squawking ident. This would ordinarily provide an identification detail on the radar scope in KK Approach. However the Radar controller came back saying "WS, negative, you are not radar identified."

I wasn't exactly frazzled, since I understood that positive seperation and air traffic services could still be provided procedurally if KK Radar could not "see" us. It would just require a little more work tracking us by making annotations on a "flight strip", that little piece of paper with a summary of our flight plan where the air traffic controller could monitor our progress. If I am mistaken, the sages of aviation can correct me.

At about 30 miles outbound, albeit a touch early, KK Radar called in and transferred us to Labuan Radar. The check in with Labuan Radar also revealed us as not radar identified. However, the controller continued to direct us to Maersk VIking and instructed us to call ready for visual descent.

As we went on our merry way, I made a cursory check on the Minimum Equipment List. There was nothing definitive in it about a Return To Base should the transponder fail. In fact for all internal indications in the cockpit, we were flying with a serviceable transponder! 

On our return leg to Kota Kinabalu from Maersk Viking, I considered our radar visibility to other aircraft in our shared airspace. We listened to various radio transmissions from fighter aircraft and helicopters from the army, navy and air force in chatter with Labuan Radar. They were prepping for military exercises over Labuan waters for the next day. I decided that after the return to KK under procedural control, I would snag the aircraft. It would not be right to leave the transponder unattended to by the engineers with sorties coming up the next day in such proximity to the airspace being used for the exercise. Hazardous. Flight safety first!

I expect that I gave the engineers and the Base Flight Safety Officer a bit of a long day that afternoon for having snagged the aircraft and raising a flight-technical incident report. The aircraft was rendered serviceable for the next day and as far as my checks with KK Helibase went, the crew of the following day flew unhindered by the transponder. I was a touch smug. Affirmation!! Vindication even!

Then came 11 March. I was due for a single sortie that morning. Fridays and weekends are rather low key. The destination rig was Malikai. Nice for a Friday, just an hour and some minutes and then home. However, once again, upwind from Runway 02 Kota Kinabalu, checking in with Kinabalu Radar brought a repeat of "WS, you are not radar identified." Squawking ident was to no joy. However, Malikai was just another twenty minutes out and in relatively safe airspace. The revenue flight continued under procedural control to its conclusion and post landing I had a word with the engineers. I snagged the aircraft again and raised another incident report.

The engineers were baffled at the recurrence. Another late evening. The following morning, ground functional checks using their test kits showed that the transponder was indeed active. But seeing that they also had a scheduled leak check to carry out with the rotors running, they had me summoned for an engine ground run. Running through the checklist items, I attempted a check with Kinabalu Tower for the transponder. And of course I was not radar identified. After shutdown, I brought this up with the engineers, with a rather grave tone of voice. I did not snag the aircraft, hoping that they could resolve this out of the books.

One of them postulated that perhaps the transponder works only in flight. I did not raise an argument because theoretically we should be detectable to other aircraft even on ground. I had seen the amber "traffic" annunciator flash on screen often enough. If I am mistaken, the sages of flight can reeducate me.

The chief enginner called for a flight test. Great. That would put the matter to rest, wouldn't it? Arrangements were made, flight plans were filed and soon we were up in the air with two engineers in the cabin to watch and hear the proceedings. As soon as we were airborne, I called in to Kinabalu Radar:"Confirm we are radar identifed?"

"WS, you are radar identified upon passing 200 feet."

We spent 25 minutes on the downwind leg to accommodate other arrivals and soon were back on the ground, happy and confident that an engineering breakthrough would see the flight of the coming week executed without a hitch. Indeed, I was scheduled for the next day for two long flights into Labuan waters where radar control was imperative.

As it would happen, the very next morning after getting airborne for Gumusut, the radio chatter from Kinabalu Radar was "WS, you are NOT radar identified......"

Yes, it seemed to be me, not the aircraft.

And yes, I got chewed up on the return to base by both Radar and Tower. Kinabalu Ground was the only friendly voice that day.

Some days, you can just never win.