On The Airbands

And myself always being on the lookout for a good diary, I found a real gem in the Skytimer Pilot Organiser at the airshow. Publisher Karen Mahlab and her pilot husband decided there was a real need for a pilot diary/directory. One book carrying all the info pilots seem to like to carry around on endless scraps of paper. After talking to commercial pilots, private fliers, helicopter pilots, the Skytimer Pilot Organiser was designed, and they’ve done a great job! This great little diary contains an organiser/ diary section, tabbed info sections, an operational section, plus general section including measurement conversions and emergency procedures and codes. And the diary comes in either desk or pocket size from Mahlab Information, 81 City Road South Melbourne 3205. You can phone enquire on (03) 629 3456.

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Qantas flights near the UK are now using VHF phone patch facilities available through Portishead Radio (run by British Telecom) on frequency 131. 620 MHz. The service has been inaugurated for all airlines without existing VHF phone patch arrangements.

And reiterating that the old Qantas training VHF of 126. 7 has definitely been surrendered to the CAA on an Australia-wide basis as Australia’s very first Unicom frequency.

Three Qantas 747-438 aircraft have now been fitted with satellite antennas to enable an exchange of data and voice information through the ln Marsat-B satellite system. An OTC earth station is now fully operational located in Perth.

And it’s a heartfelt thank you to Captain John Carver and Second Officer David Sear, and Flight Service Director Kathryn Nicholls from the Qantas 11/New Zealand 340 nonstop service to Los Angeles from Sydney on which we were passengers. T he

service is frankly still second-to-none, and in addition we were

singled out and treated to a grand tour of 747-438 VH-OJK from stem to stern. We even got to check out the Flight Attendant crew bunks located near the tail on the main deck!

And thank you also to Peter Shakells from Qantas Operations Information and Communications, whose spies heard we were pax on the aeroplane, and who alerted the crew to our presence. Much appreciated. And just by chance, VH-OJK was the very aircraft involved just two weeks prior to our flight when I conducted an inflight Skycoms broadcast interview with Captain Allan Ross and the crew of Qantas 27 bound for Hong Kong for an FM radio station I also work for. An uncanny twist of fate!

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Eric Giddio from Mascot NSW writes and details the hours he spends listening to aircraft radio. It’s surprising you have time to eat and sleep Eric!

T his is another amusing incident involving an Asian crew, and also stars on this occasion an Australian Airlines 737-400 crew, flying VH-TAY. T he foreign aircraft involved was Korean Air flight 671, and its radios were apparently unable to be tuned to transmit or receive on either of Sydney’s Approach frequencies 124. 4 or 126. 1 MHz. So VH-TAY the Australian 737 met Korean 671 on frequency 121. 5, the aeronautical distress channel, to relay approach and landing clearances from the ground stations. I might just add here before we start that 121. 5 is frequently used for this sort of operation when an aircraft partially loses comms. But once the vital messages have been passed, ATC r-e-a-1-1-y appreciate it if whoever has been using it shuts up quickly so any imminent emergencies don’t gounnoticed with survival beacons drowned out by unnecessary voice traffic.

VH-TAY : (relaying) “Korean 671, this is Tango Alpha Yankee, you are cleared to descend to 5,000ft, report established on the one six localiser!”

KOREAN 671: “Roger roger . . . report established”

VH-TAY: “Now descend to 3,000ft, and you are cleared for final on the one six localiser”

Korean Air 671 acknowledges, and at this point everything appears to be going well with the little airborne three way relay between ground stations, VH-TAY, and Korean 671. But of course, the crew of VH-TAY have to land their plane too. T hat’s when things turn a trifle sour!

KOREAN 671: “Korean 671, established localiser railway one

six”

VH-TAY: (after a while) “Say again Korean!”

KOREAN 671: (puffed) “Estabrished locariser one six”

But once again VH-TAY was busy with its own landing and didn’t acknowledge the Korean airliner, so Korean 671 continued KOREAN 671: “Ahh . . . this is Korean 671, we are now estabrished on locariser one six, over!”

Things now start to hot up . . .

KOREAN 671: “Tango Alpha Yankee, this is Korean Air 671, confirming landing permission, landing permission for landing rahway one six”

VH-TAY: “Ahh . . . go ahead Korean”

KOREAN 671: “Confirm clear, clear landing runway one six” VH-TAY : “Err . . . from West Pymble, from Whiskey Papa Bravo, you are cleared for final on the one six localiser”

KOREAN 671: ” Roger . . . understand . . . but confirm landing permission, landing permission for runway one six so now . . . err, only 1,500ft from one-sixer, so . . . landing permission!”

VH-TAY: “Korean 671, standby!”

KOREAN 671: “Korean requesting landing permission runway one six, over”

VH-TAY: “We’re still awaiting the clearance Korean!” KOREAN 671: (shouts) “Go ahead, go ahead!”

VH-TAY: (with hesitation, obviously monitoring 120. 5 Sydney Tower and taking Korean’s landing clearance from that station) “Korean Air 671, you are cleared to land runway one six” KOREAN 671: “Roger, cleared to land runway one six, tang you!” VH-TAY: “That’s affirmative, cleared to land”

KOREAN 671: “Tang you, tang you!”

After landing, the following was transmitted by VH-TAY VH-TAY: “Korean 671, shut down all radios now, shut down all radios now”

KOREAN 671: “Roger, tang you, can I make another call?” VH-TAY: “Negative, shut down all radios, no further transmissions!”

But against all this advice . . .

KOREAN 671: “Roger roger, tang you, tang you . . . for your cooperation”

UNIDENTIFIED: ” Yeah . . . we got him mate!” A footnote from Eric Giddio states that he actually saw VH-TAY come over his house, and says that the Australian Airlines 737 was passing messages to Korean 671 while the 737 itself made a landing on the crossing runway, RW 25.

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Many readers are asking more questions about AGARS decoding, so here are the answers to the most commonly asked questions. The type of data modulation is MSK,or minimum shift keying.

FSK modems will only print out garbage if used for AGARS decoding. Speed is 2,400 bits per second, and the audio carrier is 2,400 Hz. As bits are transmitted, the 2,400 Hz carrier indicates no change in state of the bits. However, a carrier of 1,200 Hz does indicate a change in state of the bits.

MSK modulation is essentially a form of “packet radio”. When an aircraft is ready to transmit, it monitors the radio channel for a busy. If there is no traffic, the aircraft transmits. If the ground station receives the message without errors, it transmits an acknowledgement. If no acknowledgement is detected, the aircraft retransmits the message after a delay. The protocol uses bit check sequences for error detection.

Regarding receivers, Realistic and Sony receivers that I tried out tend to have audio filtering designed to drop the sidebands. 1 have personally only had success with a Regency Digital Flight Scan (an antique scanner) given to me as a gift by my counterpart in the USA, aviation radio columnist Jean Baker of Monitoring Times magazine. The waveform required by AGARS is preserved by this receiver, whereas the audio from the Sony Air-a and a Realistic PRO-2004 produced distortion of the AGARS signal. Square wave signals have to be produced by a Waveshaper for success, and the Waveshaper used was made up from parts cannibalised from the FSK modem which had earlier failed to work with AGARS. The square wave signal was fed into pin eight of the RS232 port on my computer, to let the program software 1 was using take over. Frequencies for AGARS are at present 131. 550 and 130. 025 MHz.

One more interesting fact. Some messages are automatically downlinked. Messages such as when the cabin door is closed or when the wheels retract after takeoff. In these instances, switches close and the “doors closed” and “off-report” messages are automatically transmitted without the tech. crew having to physically key them in and send them.

Used with the appropriate software, which has a “filter” element written into it to allow the rest of the program to activate when it detects a 2,400 Hz carrier, you can decode ACARS. If you use a program without this “filter” written in, the main program will start too soon and will most likely be out of sync. with the data being transmitted!

Aeronautical Radio Incorporated of the USA (ARINC) produced a 100 page volume in 1983 entitled ARINC Communications Addressing and Reporting System. Perhaps anyone interested enough could write to ARINC in the USA for more information.

Assuming some of you have come in late on this. . . ACARS means “Aeronautical Communications Addressing and Reporting System”, and is an addressable digital datalink permitting message routing to and from a particular aircraft, through VHF stations, or by satellite link. Downlinked reports include departure and destination times, engine monitoring data, delays, positional and in-range reports, and also winds aloft observations on INS, IRS or GNS equipped aircraft. Uplinks include selcal, load and weather data. In the US alone, there are over 150 VHF ACARS stations in full operation. However, if ACARS are satellite-sent. forget any thought of monitoring them!

Troy Jacobsen from Thuringowa Queensland was recently monitoring Townsville Tower frequency 118. 3, when he overheard the following conversation involving the Tower, a Piper Warrior, a Twin Otter, and five RAAF F/A-18 Hornet jets.

The Warrior (VH-TEE) called ready for takeoff from RW 01, followed closely by Australian Regional Twin Otter VH-TGH, who was ready at the centre taxiway. Both aircraft are instructed to hold position, due to Hipshot 5, the formation of F/A-18’s, about to depart.

VH-TEE: “Townsville Tower, Tango Echo Echo ready!”

TOWER: “Tango Echo Echo hold, a short delay” VH-TGH: “Tower, Tango Golf Hotel ready”

TOWER: “Tango Golf Hotel, hold position, short delay due military aircraft departing” HIPSHOT 5: “Tower, Hipshot 5 ready”

TOWER: “Hipshot 5, clear for takeoff, make left turn”

Five RAAF F/A-18 Hornets then make a very spectacular formation departure.

Then. . .

TOWER: “Tango Golf Hotel, clear for takeoff, make left turn”

VH-TGH: “Tango Golf Hotel roger, watch this!” (the aircraft then making a very normal departure)

TOWER: “Ooh. . . very nice Sir!”

VH-TEE: “Yes. . . the sheer speed and power involved was just awesome!”

VH-TGH: “We’re just handing out the neckbraces now for the passengers who received whiplash from the sustained G-forces!” Gotta be the Intercept-of-the-Month! Thanks Troy, and make sure you write again.

From Lismore NSW, and our regular correspondent Halden Boyd. Ansett company frequency 130. 6 which was used over northern NSW by a Brisbane bound Boeing 737 VH-CZM, and overheard by our plucky correspondent.

VH-CZM: “Ahhh. . . we have a slight problem. The hosties can’t get the First Class number one and two stoves to heat the meals. Can we have that checked when we arrive? We’ll also require three wide wheelchairs, and can you advise the outbound crew taking over this aeroplane at Brizzie that they have one additional crewmember on board”

ANSETT GROUND: “Roger, I’ll advise the Engineers, and there will be three wheelchairs waiting. But we weren’t expecting any extra crewmembers. can you elaborate on that one?” VH-CZM: “She’s a work experience girl!”

ANSETT GROUND: “How’s she going. . . is she any good?” VH-CZM: “Lovely manners. . . and legs to match!”

Monitored by your author on Ground frequency 119. 9 at Bank-stown Airport. An American voiced pilot speaks to the Controller enquiring “Why can’t my class of operation be approved for a Runway 25 Simops arrival at Sydney Airport?”

GROUND: “Your category of operation is unsuitable” PILOT: “Why?”

GROUND: “Well, after a rather nasty incident some two months ago at Sydney involving Simops, our guys there are just sick and tired of aircraft on the cross runways doing their best to T-bone Boeing 747’s and DC-10’s using RW 16 or 34!” That ended that little discussion just like that!

Margo Woolard (Maggie) from Nunawading in Victoria wrote to me recently re her intercepted “Mayday” call from a US-bound 747-400 (not Qantas I stress!) which had departed Sydney some hours prior for Los Angeles Airport.

I must confess I was a little skeptical that the call was actually as reported, as Maggie admitted she is a relative newcomer to the hobby. But it would appear I owe her an apology, as a discussion I recently had with a Qantas Captain detailed an amazing story of a foreign airline’s B747-400 fuel management computer jamming up and causing a potentially dangerous situation to occur for those on board.

A freak problem with the computer on board prevented the crew from managing their fuel by transferring from tank-to-tank,

as is normal operational practice. The crew found in fact that they could not use any fuel apart from the tanks they were drawing from at the time, which had approximately 90 minutes of fuel left all up. Things began to look bleak, as the airliner was still 4 hours 50 minutes or so from the nearest airport, let alone a 747 capable airport!

Phone patches to their company in the US, and Boeing in Seattle provided the vital computer information to unlock the fuel management computer control, and allowed them to access the other fuel tanks on board and continue the flight normally. The frequency 5574 kHz was apparently tied up for about an hour and a quarter as the airliner spoke to San Francisco Radio, and had the phone patches initiated on their behalf. The Qantas Captain, who was flying Qantas 11 on the same route as the stricken airliner, could not speak highly enough to me of the sheer professionalism of the foreign crew, who did an immense job under very trying circumstances.

Thank you Margo Woolard, and keep up the good work!

That’s all we have space for this issue. To become a part of “On the Airbands”, write to me. . . Bob Bell, at PO Box 16 Georges Hall 2198. Please indicate if you wish to be credited for your contributions. Unless you do, I have to assume I can run your name and details in the magazine. For replies, a stamped self-addressed envelope is appreciated, as postage costs have climbed to FL 450!