Waltzing Wingtip to Wingtip into San Francisco Airport

By Capt. G A Fernando MBA

gafplane@sltnet.lk

RCyAF, Air Ceylon, Air Lanka, SIA and Sri Lankan Airlines.

The four engine Airbus A340 was designed for ‘long, thin’ routes and therefore was the ideal aircraft to be used on scheduled flights from Singapore to San Francisco, USA, via Seoul, Korea. The SIA Boeing 747s have been operating via Hong Kong, for some time before that. The objective was to provide a convenient route for Indian traffic among others, bound for the ‘Silicon Valley’ in California, USA. Unlike the Marketing Division in our national carrier, which worked only from 9 am to 5 pm, Singapore Airlines’ own division analysed permutations and combinations of traffic patterns 24/7 to provide ‘bottoms on seats.’

I had done a few flights to Seoul before, but never beyond. 21st December 1998 found me and my crew flying from Singapore to Kimpo airport, Seoul, on the first leg of my first flight to San Francisco. The second leg being longer, across the Pacific Ocean, we needed a second Captain to provide inflight relief to me and my First Officer. I had not met my co-captain, Ian before. There was a ‘Pub’ across the road from the Seoul Hilton called the ‘Red Rock’. As it was customary, my First Officer and I went there for a pint of beer before dinner that night and bumped into him. After our introductions, I casually asked him whether he had operated to San Francisco before, since neither my First Officer nor I had ever operated there before. He too had also never operated there. We had good laugh and declared that it was bound be an interesting flight.

The next night our departure from Seoul was uneventful except for the fact that on our climb out we had to do a quick turn left to avoid the De Militarised Zone (DMZ) and ensure that we did not overfly the Presidential

Palace the breach of which would have got us shot out of the sky as mentioned in our Departure charts. (Two tracer warning shots and the third one was for real). Our route took us over northern Japan and then across the Pacific was rather smooth. One way of finding out whether our ride was going to be smooth or turbulent was to tune to 123.45 MHz which was the air to air frequency. If there was chatter of pilots warning each other of the presence of patches of turbulence that would mean a rough ride. If the frequency was quiet, then all was well.

We had lots of time to study our arrival charts in detail and my landing briefing (based on my experience) ended with something like this “Gentlemen, none of us have operated into San Francisco before, therefore we will stick to our Standard Terminal Arrival Route (STAR). We will not declare that we have the runways in sight too early as we have to be certain of our position and not misidentify the runways”. Fortunately, though windy, it was clear weather. In pilots ‘jargon’ CAFB (Clear As a F……g Bell).

“Ian, take a look at the Taxi chart and guide us to the parking stand please and if you are not happy of the situation at any time. Just sing it out loud!”

These were the days (22 years ago) of paper charts. We had yet to graduate to GPS position on ground overlay on an electronic display of the charts, like in electronic tablets in the ‘paperless flight decks’ of today.

Our descent took us past the Golden Gate Bridge with a great view of Alcatraz and then San Francisco Radar brought us over the airport at 11000ft clear of Oakland area air traffic. (I had been warned about this by my friend and neighbour Rohan, back in Singapore). Then we had to descend quickly to 6000ft, after which we were instructed to turn perpendicular to the final approach for runway 28 Left, known as the ‘Left Base Leg’. We could also see another aircraft doing the same from the other side of the airport for Runway 28 Right, known as the ‘Right Base Leg’. Now we were facing each other (with all our lights on) and virtually playing chicken! (Actually they were cleared to 7000ft) Then we were instructed to establish on the final approach of Runway 28 Left while the other aircraft was instructed to establish on Runway 28 Right. (Parallel runways) I slowed down to the slowest possible speed so as not to overshoot the extended centre line and on to the path of the other traffic (Now identified by us as United Airlines).

Flying to parallel runways was no big deal. We Sri Lankan pilots had been doing it for years in places like Frankfurt, Germany. Usually one runway is used for landing while the other is used for take-off, except if the following aircraft inadvertently, got too close to the aircraft ahead. Then the controller would ask pilots of the leading aircraft to call when they had both runways in sight. As soon as that was declared, the controller would instruct the leading aircraft to swing to the parallel runway. The leader and the follower would land almost together.    It could be done safely as the Frankfurt runways were also well spread out (3000ft) compared to San Francisco which were only 750 feet apart.

Controllers are forced to bring the two landing aircraft in formation very slightly staggered, virtually wingtip to wingtip, with the smaller and thus lighter aircraft ahead, because of the presence of wing tip vortices. The wingtip vortices are produced in flight as a result of the mixing of high pressure air at the bottom of the wing and producing the force of lift, mixing with low pressure air at the top of the wing at the wing tips, resulting in a wave like wake of a boat. The turbulence thus created rotates inwards, spreads outwards and downwards within a few seconds. The aircraft have to virtually fly wing tip to wingtip to avoid the adverse effect of the created turbulence. Wake turbulence, is proportional the weight of the aircraft. As a result of this wake avoidance consideration, the aircraft on the right is framed on the First Officers windscreen! The larger aircraft trailing behind is not allowed to overtake the other, but has to maintain its position till touchdown. The pilot flying the approach has to maintain the centre line of the runway, reinforced by their instruments, but also keep a visual lookout for the other aircraft which is darn too close!

That day, it was a bit gusty and our wingtip to wingtip waltz began.  We were still not sure where exactly our landing runway was. The runways are very close together.  So when the Control Tower asked us whether we had the other traffic and the right hand side runway in sight, we replied that we had a visual fix on the parallel traffic but denied that we had the runway (as per my briefing). Then the tower gave us a heading outward and away from the runway centreline, presumably before getting us to ‘abort’ the landing approach, and go around. So much for my briefing! My First Officer then declared “San Francisco Tower now we have the runway 28 Left in sight” The Tower’s response was to proceed visually and land.

Legally, until the pilots declare that they have the runways in sight, it is the Air Traffic Controller’s responsibility to maintain separation with the other aircraft. The whole approach was very exciting.  Ian with the help of his Taxi Chart guided us to the parking stand. This was first of many flights I did for over four years, on the average of about one a month, on the Airbus A340.

Since that time 22 years ago the situation had somewhat changed for the better, with the introduction of Precision Runway Monitored (PRM) approaches which involve a second dedicated Air Traffic Controller, who solely monitors a ‘no transgression area’ between the two runways on a high resolution radar and give instructions to pilots who are listening out to him in addition to the Control Tower on runways that are less than 3000ft apart. If an aircraft drifted unintentionally to the ‘no transgression zone’, it would be immediately advised and required to break away and climb out. These PRM approaches are practised regularly in Simulators by the Airline Pilots who will be required to fly safely into these airports that entails flying to a greater degree of accuracy.