Archive for parallel runways

How do YOU land at San Francisco International Airport?

Posted in air travel, airline, airline pilot, airline pilot blog, airliner, airport, flight crew, jet flight with tags , , , , on July 9, 2013 by Chris Manno

sfo 2

Here’s how you land at San Francisco International. First, the view over your left shoulder as you cruise “downwind” for your arrival into San Francisco International. You’ve arrived from the Pacific side of the airport, so you can plan (they’ve probably advised you already) on landing on runway 28L, which is the runway you’re paralleling on downwind. Yes, there are 2 runways that you are paralleling, but the logical one for you is the one on the left. Here’s what the airport diagram looks like, with an arrow pointing to 28 Left:

sfo 10-9a

Let’s talk about all of the runways at San Francisco International (SFO), because their are simultaneous operations on all four runways, so your landing runway is not operating independently or simply–nor are you as a pilot landing at SFO. Those two runways intersecting your landing runway will be launching aircraft out of SFO even as you are landing: yes, they’re crossing your runway–and you theirs–simultaneously. That means the SFO tower controllers are managing a complex ballet of speeds, timing and clearances. They’re doing a precise, excellent job, but a lot will depend on you: you must fly the assigned airspeed exactly in order for all of the moving parts in this synchronic mix of flying metal to mesh smoothly.

sfo 1a

But wait, there’s more: runways 28 left and Right are too close together. Built built on a man-made pier, the pair are crammed closely together, closer than the standard, required spacing for parallel runways. Why does that matter? Well, because on final, aircraft approaching the runways at the same time will fly closer than the normal lateral separation required by the FAA standard:

28 parallel

Not taken with a telephoto lens. Rather, that’s a jet landing on 28L, taken from the cabin of one landing on 28R.  Lateral separation is minimal–by virtue of a waiver of the standard separation that the FAA granted to SFO–so there are more restrictions on you, the pilot. First, you must not overtake the other aircraft. That’s because the trailing aircraft is charged with maintaining visual separation, because the leading aircraft can’t really see the trailing aircraft. If you overtake him, there will be a period where neither can maintain separation visually. So airspeed control must be exact, usually assigned by tower–to ensure separation from another part of the moving mechanism: aircraft are taking off on the intersecting runways, shooting the gap between your landing aircraft (and the parallel partner above) and the ones who landed before you.

Here’s the instrument approach for your landing runway–and there’s a complication today with that, too.


Today, the radio glidepath, or “Glideslope” (GS) is NOTAMed (NOTice to AirMen) out–meaning you will not have that descent guidance available on your display, so, you’ll be expected then to manually crosscheck the “step down” altitudes (7000, 6000, 5000, 4000, 3100, 1800, and 213) against the distance marked on this chart. All while flying the specified speed assigned by tower, which you must integrate with the maximum speeds allowed by the flap configuration required for the approach and landing.

bug eye cockpit

Sounding too complicated to manage? Well, it’s not. In fact, it’s routine: very often, you’ll encounter intersecting runway operations (Chicago O’Hare comes to mind, and those controllers do a fantastic job of choreographing that ballet); many airports have reduced, FAA-waived runway separation (hello, Minneapolis), and at any given time, airports around the nation report various instrument landing system components temporarily out of service .

The glideslope being out wasn’t a surprise, either: you were advised by NOTAM (see above) before you even took off on this leg of the condition of the equipment and on your approach briefing (probably done within the last hour) you reviewed the requirements, procedures and complication with the other pilot(s) in the cockpit prior to starting the approach.  And if you’re savvy,  just in case, you briefed the approach to the parallel runway as well. That’s because at any point, due to traffic load or other factors, SFO tower can swap you to the other runway–just like that but again, that’s routine in the airline biz. Expect it, pre-brief it, deal with it.

fms crz

Which means reprogramming the correct approach points in the Flight Management System (FMS) on the fly (pun intended) and verify each point, then set up the correct intercept to a forward waypoint in the FMS. All the while, don’t forget our friend out there–it’s your responsibility to stay clear–

28 parallel

Fly the speed assigned to the waypoint assigned, maintain the altitude minimums according to the above chart by comparison with your distance from the field and . . . configure for landing, while observing the flap speed limitations of your jet.

Here’s where you get to do your own balancing act within the swirling gearbox of approaches, landings, takeoffs and climbouts: if tower assigns you to fly a speed of 200 to “DUYET,” (see approach diagram above), that means you are limited to flaps 15 (have to be below 190 for more). But DUYET is at 1,800 feet and your airline has a “stabilized approach” policy below 1,000 feet: must be in final landing configuration and stabilized airspeed (neither increasing or decreasing) with a stable power setting (neither spooling up or down) from 1,000 feet to touchdown.

Power control is key to airspeed.

Power control is key to airspeed.

From 1,800 at DUYET to 1,000 feet, at a standard descent rate of around 800-900 feet per minute, you’ll have about 60 seconds, maybe less depending on tailwinds, to decelerate about 50 knots, then re-stablize the speed and power, and extend the flaps from 15 to 25 to 30 or 40 for landing. If not, mandatory go-around–meaning, initiate a climb following the “Missed Approach” instructions on the chart above. That’s also included in your approach briefing, remember which one–left or right–that you’re doing because remember, there are aircraft launching as well, mixing into the airspace. Then either repeat the approach (also very routine) or divert.

Stabilized? Good–now the only thing YOU must do is monitor descent rate, speed and alignment. That’s why a stabilized approach is vital: being set in descent rate and airspeed and power setting frees you to simply fly to a safe landing. After an approach that you now know is anything but simple. Happy landings.

737 landing crop

Jet Wake Turbulence: Distance Ain’t Enough.

Posted in air travel, airline, airline pilot blog, airliner, jet, jet flight, passenger, pilot, travel, weather with tags , , , , , , , , , , , on January 19, 2013 by Chris Manno

Sneaking up behind me, are you? Here’s an infrared view you might need to heed: not the hotspots, but powerful the twin horizontal corkscrews of air current swirling off the wingtips of my jet. They’re wily, dangerous, and not to be trusted.

According to the Flight Safety Foundation, the vortices from a jet can have an internal rotation of up to 300 feet per second and often extend between 2 and 10 nautical miles behind a jet aircraft. The twin tornadoes–that’s literally what they are, horizontal but spinning powerfully–sink at a variable rate, between 300 and 500 feet per minute to an altitude  between 500 and 900 feet below the aircraft’s flight path and can persist for three or more minutes depending on the meteorological conditions.

That’s the problem, but hardly the full situation. Add to this hazard the closely constrained flight path of jet traffic in terminal areas. For instance:

SFO Q bridge

Approaching from the east, you’ll have a traffic stream from the west as well converging on the same runway complex. Not unusual as far as airports go–except that San Francisco International has less than the standard distance separating the two parallel runways. The FAA has waived the normal lateral separation, but you’d better keep that in mind nonetheless because that also means less than normal separation from the vortices of the aircraft next to you. Remember the outward spreading motion of those two tornadoes?

747 BAThis guy could be your dance partner all the way down final–and if he’s next to you, you aren’t entitled to the separation you’d get if he were ahead of you. Mostly, ATC will “advise” you to “use caution” for the heavy on the west runway, workload and time permitting–but they don’t have to.

And time and workload may not permit any advanced warning, and adverse weather can shroud the entire scene anyway:

SEA 16CLook at the inset on the bottom right corner: Seattle (one of my favorite destination cities!) has three parallel runways grouped together, and you won’t be told which of the three runways you’re landing on until you turn base to final about three minutes from touchdown. Would it make sense or even be possible to keep you informed of the heavies on all three inbound tracks? Add to the mix the typically obscured Seattle visibility, plus the added workload of programming and validating the FMS  sytem approach waypoints at the last second demanded by the late runway assignment and is there a possibility of situational awareness overload, on final approach: was that a heavy in front of us? Or on the outboard runway?


Bring that back to San Francisco, where the standard runway separation is “waived,” like in MSP and many other cities. Now you’ve got a “buddy” laterally whose wake turbulence is drifting outwardly–just as yours is–and just because he’s not a “heavy” doesn’t mean he can’t roll you.

The ICAO worldwide “recommendation” for separation between a “heavy” and a “medium” following aircraft  (say, a 747 and a 737) is 5 NM (9.3 KM); between two heavies, 4 NM (7.4 KM). But the wild card not even mentioned in the separation rules is configuration and maneuvering: simply put, a “dirty” jet (flaps, gear) creates a nastier wake than a “clean” jet, and maneuvering distorts weight. That is, if I level off my 160,000 pound 737 with an addition one-half “G” force, I add to the effective weight another 40 tons of effect. And we’re a medium jet–imagine a heavy maneuvering dirty adding to his effective weight and wake.

That’s the science, now here comes the art. You know the reported winds at the field, but that’s a red herring: your encounter with wake turbulence won’t happen on the field. You need to be aware of the winds on approach, at your altitude. If the lateral wind at your altitude is blowing into the other jet’s wake, here’s what can happen: if the drift equals the outward spread momentum of the wake–and you have to figure the “dirty,” “maneuvering” wild cards mentioned above–the effect will either be to move the wake away more rapidly, or freeze it in place till it dissipates. Which is it?

You can’t see wake turbulence. You can’t be sure where it is, or know it’s strength based solely on the aircraft designation. And sooner or later, you’ll find yourself in it despite your best, most diligent precautions. What are you going to do, captain?

dusk b

For a true jethead like me, the first answer is always speed–but not so fast (pun intended): you’re configured with restrictive maximum flap speeds. If you’re in a final configuration with 40 degrees of flaps, you’re limited to 162 knots max. But the second instinct is valid: power.

throttle bugeye

But power alone is only part of the answer: what you’re not doing is going down. Why not? Because we know the vorticies are sinking. If we remain level or climb, we’ll escape the effects. What are they?

The Flight Safety Foundation survey of hundreds of wake turbulence encounters reveals uncommanded roll in trailing aircraft of up to 45 degrees at altitudes below 1,000 above the ground. One thousand feet is another magic number at my airline: stabilized approach  (on speed, on altitude, power set) is mandatory from 1,000 feet to touchdown. On glidepath–not above or below; not accelerating or decelerating, power set to flown speed and stable. And certainly wings level.

Which brings up the next problem of two major headaches you’ll instantly own. First, the right amount of counter-aileron, even if applied prudently, in many jets will bring up the wing spoilers to drop the low wing rapidly, inducing adverse drag, requiring more power.

Second, the option of climbing or even flying level is constrained by the published missed approach: protected airspace may be below you if you are above the missed approach altitude. And laterally, not only is there often parallel traffic, there’s also dangerous terrain you must always monitor and stay clear of:


If you encounter wake effects in a level portion of the approach segment, prior to the aircraft ahead descending, at least you know his vortices will descend eventually below you and in this case, you normally feel the “burble” which now cues you: if the winds are keeping his wake aligned with your flight path, on glidepath you’re likely to fly into the tornadoes again when you’re slow and configured with speed-restricting flaps. Now look at the “mileage separation:” still think distance alone is enough? Still committing to the glidepath?

All of that doesn’t even consider the added, inevitable spoiler in every approach: weather. There’s more than terrain and aircraft for you to avoid in a very constrained airspace.


There’s really only one good answer: up. And “up” may be a s simple as “no more down,” meaning a stopped descent or a slight climb to exit the effects. In any case, if you’re below 1,000 feet you’re no longer “stable” per the mandatory requirements. If you’re above 1,000 feet, you’ve just been cued that the mileage interval, given the meteorological conditions, nonetheless has left you vulnerable to the adverse effects of wake turbulence–and you’re not going to proceed.

Which means, in the immortal words of my old friend the Chief Pilot at my airline addressing my 1991 class of Captain’s “Charm School” (officially, “Captain’s Duties & Responsibilities”) as we sat rapt: you’re going to “get the hell out of town.” Amen.


Back in the cabin? Expect the usual complaints about the delay for the second approach, plus a regular dose of exaggerated “there I was” tales about their wake turbulence encounter. So, don’t tell them–if you’ve done your avoidance and even escape properly, they’ll never know you even had a problem, which is the ultimate goal anyway: detecting and avoiding the problem in the first place.

The end result is, what they don’t know won’t hurt them, because you won’t let it. And that’s kind of why you get the privilege of flying the jet in the first place, isn’t it?



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