Chapter 12 — Light Streaks Off The Runway

Le Minh Kha heard a strange signal at 2:07 a.m., between two calls for the parking lot.

Signals are not like speech. It is a short series of sounds, inserted into the internal channel and then lost. Kha thought he heard wrong because the duty room had a dehumidifier running continuously. He took off his headphones and listened again from the recording. The tone sequence appears twice, fourteen seconds apart.

Kha called the tower. “Duy, did you hear the signal on the apron channel?”

Duy immediately replied: "Time?"

“Two-seven, two-seven-fourteen.”

“I checked.”

Kha wrote it down in the notebook, then hesitated in front of the reporter box. You can write your name. You can also leave it blank like many previous pages. He wrote.

At the tower, Duy opened the radio record. The signal does not go through the main operating channel, only enters the apron channel. It resembles interference from a handheld transmitter, but the frequency is slightly off. Duy reported Nghi.

Nghi arrived at the duty room at 2:35 a.m., bringing Uyen with him. Open the record. The sequence of sounds sounds like three short beeps, one interval, then two long beeps.

“What device is on?” Nghi asked.

Kha refers to walkie-talkies. “Four. One charger. Vehicle code scanner.”

“Is there anyone out of the area?”

“Not according to the list.”

Uyen asked: "Is the signal related to the light?"

Do not answer. She told Kha to record it as an unusual signal on the apron channel, source unknown. Duy agrees.

The next morning, Tong heard the report and wanted to classify the signal as "communication interference".

“Is there proof it's not noise?” he asked.

“No,” Nghi replied.

“So why include it in the W-3 report?”

“Because it appears near the time of Circuit Check Report and can be a source of communication confusion.”

“Maybe too much.”

Kha stood next to the table and said: "I listened to it three times last week. Only this time I wrote it down."

Tong looked at him. “Why wasn't it written before?”

Kha can't avoid it. “Because I think if it doesn't have a direct impact, no one will read it.”

Keep quiet. The answer comes down to something bigger than a radio signal.

Nghi requested to open the apron shift book for three months. Lines stating "strange sound", "spontaneous walkie talkie", "hearing unclear signal" appear scattered. No lines have full timing. But when compared with rainy days and generator running days, they cluster around times when the source changes.

Duy said: "Maybe the light controller is causing interference."

Uyen asked: "If it causes interference, will it cause false signs?"

"Not necessarily. The two systems use the same source but different signal paths."

Nghi went to the electrical cabinet and checked the filters. All intact. She did not turn the signal into the cause of the streak of light. She put it on the list of questions.

“We need to know when it happens, not just what it sounds like,” she said.

Kha accepts the time finding part. He called the people who were on duty. One remembers the signal that appears when switching sources. One person said it was the sound from a forklift. One person said he didn't want to answer because he was on leave and didn't want to get involved.

No pressure. He asked if they would agree to provide hours and locations. Some people agree to remain anonymous.

Uyen made a comparison table. Time column, power, rain, circuit status, listener, record. She discovered a commonality: the signal usually appeared within the first two minutes after the transmitter received the load.

Tong looked at the board. “Does this signal cause the light to misalign?”

Nghi said: “There is no data yet.”

“Does it put pilots in danger?”

“If the operator misses an important piece of information, maybe."

“So do we need to close the yard?”

“Not just because of the signal. But it is a reason not to use the communication channel as an untested secondary system.”

Duy asked for permission to test run in the absence of aircraft. He placed one receiver in the tower, one on the apron, and one near cabinet W-3. The transmitter is turned on. For the first 32 seconds, there was no signal. At 47 seconds, the receiver near the cabinet recorded three short beeps, one interval, two long beeps.

Uyen turned to Nghi. “Repeat.”

Nghi asked to keep the device on and not turn it off. Duy marked the time. The light board was taken at the same time. The deflected light streak is lighter than the rain, but still appears at two corners.

The contact technician removed a filter cartridge and discovered that the contact layer was oxidized. He didn't dare say that was the reason. Just say the filter box needs to be replaced and the line needs to be measured for noise.

After listening, Kha asked: "If I replace the filter box, will everything be gone?"

"Don't know."

He exhaled. “Everyone said they didn't know.”

Nghi replied: "Because I'm in the part where I have to know before I fix it."

Kha looked at the record. “But the people on duty also heard it.”

"Correct."

“So why aren't they on the chart?”

Doubtful understanding the question is not only about the personnel chart. Those on duty, cleaning the yard, directing cars, and listening to the radio are often outside the main meetings. They have the information but are not in a position to put it into the system.

Lan suggested making a map of "who sees what". Not a title map, but a list of observation locations: towers, aprons, electrical cabinets, ditches, cold storage, patrol cars. Each location records the type of signal that can be detected and how it is reported.

Tong asked: "Does this map need approval?"

“Yes,” Nghi said. “But the founder must go from the scene.”

Tong looked at Kha. “You work with Uyen.”

Kha nodded.

In the evening, Kha stood at the apron landmark, wearing headphones. Uyen is near the electrical cabinet, Nghi is in the technical room, Duy is on the tower. When the transmitter transfers load, three beeps sound. Kha didn't wait for anyone to ask. He said: "Strange signal, time 21:16, backup power is receiving load, apron location."

Duy replied in confirmation. Uyen wrote. Nghi requested that that channel not be used for operating instructions until corrected.

The signal disappeared after two minutes.

There are no planes. No one was injured. But a sound once considered insignificant now has a name, time, location and person responsible.

On the new chart, Uyen wrote Kha's name in a box that did not exist on the old personnel map.

Kha saw it and said nothing.

For the first time, he was not beyond what he had heard.

Kha brought the newspaper channel map to the technical room and asked Nghi if he could put a recording box on the apron. The device does not continuously record all content, only saves abnormal signal markers and confirmers. Question about privacy. Kha said it is necessary to have clear regulations, not to make the person on duty the subject of eavesdropping.

Duy suggests only storing the event code and a short audio clip around the signal, with a signer. Han said the company needs to know if the apron channel is unreliable during the transfer period. Requires written approval and retention period.

Uyen wrote the process. Kha read and saw the sentence "the recorder is responsible for data protection" but there was no one to replace him when he left. He added a handover section. Nghi nodded.

“I think about the latter,” she said.

“Because I didn't know the previous part.”

The next test took place at 15:00, it was dry. Temporary channel filter replaced. The generator receives the load. No signal for the first two minutes, but a single beep appears at 86 seconds. It's not the same sequence. Duy doesn't call it fixed.

“The source could be another device,” he said.

Check if the forklift is charging. A charger emits interference pulses. They turned off, the signal disappeared. The airport eliminated one source, but could not eliminate the W-3 problem. Kha clearly stated.

“I feel disappointed,” Uyen said.

“Because it's not a light?”

“Because I want to find the right reason.”

Nghi replied: "In a real system, there can be many causes appearing at the same time. Finding an easy-to-tell cause is not always correct."

Continue reading the diary. A person on duty last year wrote "do not use the apron channel when the transmitter is on", but the instructions did not reach the new shift. No one knows where the text is. Tong asked to find the original; Vuc remembers it was posted in the old room, which was converted into a warehouse.

They found a piece of paper behind the cupboard. The ink is blurred, but there is still a warning. No effective date.

Nghi placed next to the new announcement. “This is an example of the process of living by word of mouth.”

“It lived for eight years,” Kha said.

“And dies every time the person who knows it quits.”

Duy recommends that all alerts have a code, review date and owner. Tong asked what if the owner changes jobs. Duy said there must be a successor in the handover minutes.

No one laughed when Kha took on the temporary role of signal map manager. He doesn't have a technical degree, but he has experience in the stadium and knows the sounds there. Nghi clearly states the scope of the role: collecting, not concluding.

That afternoon, Kha called Phuc, the former employee who reported the signal. Phuc said the old warning came from a time when the transmitter made the radio crackle, and had nothing to do with the lights. Kha asked if it was possible to relate to a common source. Phuc said he didn't know, but remembered that the W-3 cabinet once made a slight vibrating sound.

Kha asked for the date. Phuc doesn't remember, only remembers after a rain.

Kha does not give up information. He wrote "unknown date, memories of an ex". Duy said it was an incomplete puzzle piece, but not trash.

Looking at the map, what do you see? Kha placed the duty room, apron, tower and electrical cabinets there. Each location has a line of communication to at least two people. No one is any longer the only endpoint.

Tong asked: "If everyone reports at the same time, who decides?"

Nghi replied: "The person has authority according to the type of thing; the rest write down."

“If you don't know the type?”

“For now, consider it unclear, pass it on to coordination.”

“The word ‘temporary’ appears again.”

“This time there is a recipient and a deadline.”

Tong nodded.

That night, Kha came back on duty. A new employee heard a small beep and turned to ask if he should report it. Kha did not say "listen again". He gave the process, and the same person recorded the milestone. After inspection, they determined it was a charger. The signal is eliminated, but the record remains.

The new person asked: "If I report every time, will I be thought that I don't know how to tell the difference?"

Kha said: "Knowing the difference doesn't mean you have to stay silent when you're not sure."

Nghi listened through the walkie-talkie and did not interrupt. Kha is speaking with what he learned from the unnamed lines.

On the diagram, Uyen added a box: "person receiving information after the person reporting the end of the shift".

For the first time, he was not beyond what he had heard. This time, the whole system did not stand aside from him.