November 23, 2012

Why Are You Flying So Slow!

Flying Through Airspace Underlying the Class B

I've always been a fan of flying before dawn.  The air is smooth.  Traffic is light.  And the sight of the day's first light as viewed from the cockpit of an airliner is unlike anything you've ever seen.  Trust me when I tell you pictures do not do justice to the beauty of the real thing.  

Flight 836 pushed back from the gate a few minutes ahead of schedule.  On-time departures are another benefit of early morning travel.  Since delays haven't yet had time to pile up, flights are far more likely to depart as planned.  A Delta Air Lines A319 pushed back from the gate a few doors down and called for taxi just before we did.  The Delta jet fell in line behind a Southwest Airlines Boeing 737, who was in line behind an Alaska 737 who was in line behind a Continental jet...Airbus or Boeing...I can't remember.  One last jet was instructed to follow me as we taxied for takeoff in line with our peers.  I'll leave the identity of the last airline to your imagination for reasons that will be more obvious later in the story. 

 It was rush hour at the San Jose, California airport as we lined up nose to tail at the departure end of the runway a few minutes before the morning curfew.  Curfews seem to be popular in the Western U.S.  With airports located in such densely populated areas, departures are often prohibited before a certain time of the morning.  In addition to time restrictions, many of these airports utilize noise sensors in the areas around the airport.  Set one off and your airline will receive a fine.  I can only imagine what it must be like to live off the end of one of these runways.  No alarm clock needed, but don't EVER expect to sleep past curfew.  

In line waiting for curfew to lift in San Diego...another western city with departure restrictions.
Pilots are warned that the control tower at San Jose does not monitor the curfew.  I've never tested this, but the implication is that the tower will allow you to takeoff before the curfew is lifted...of course there's a fine for that too.  I suppose the airlines aren't the only ones intent on generating fee income.  In our case, I had my eye on the clock, and as it ticked past 6:30am, the tower controller issued the first departure clearance of the day.  In rapid succession, each aircraft was cleared to takeoff just about the time the jet ahead lifted off the runway.  

As the Delta A319 ahead of us in line received his takeoff clearance, we were told to line up and wait on the runway.  As with the previous departures, when Delta lifted off, we were cleared to depart.  Our clearance was as follows:  Fly runway heading until reaching the San Jose VOR 1.8 DME, then turn right to heading 110 to join the Oakland VOR 121 degree radial, maintain 5,000 feet.

Within seconds of lifting off the runway we were engulfed in the clouds.  Since it was still dark outside, "scatter back" from the wingtip landing lights filled the cockpit with a bright glow.  I selected landing gear up and the taxi light mounted on the nose strut began to point toward the sky then extinguished as it disappeared into the wheel well.  The Captain was at the controls and instructed me to engage NAV which would guide us around the turn to join the outbound radial of the Oakland VOR.  With the added assistance of cool morning air, our MD80 climbed rapidly toward the initial level off altitude of 5,000 feet.

My copy of the SJC9 departure...notes and all.

"Flight 836, contact NORCAL 121.3...have a nice flight."  I flipped the switch on the number one comm radio and checked in with Northern California TRACON (Terminal Radar Approach Control).  Since we were cleared to fly the SJC9 departure, there weren't any further instructions from the departure controller.  He simply acknowledged our check in and we continued along our expected course.

There's an airspace issue departing the San Jose airport that is somewhat of an unusual encounter for airline pilots...flying through airspace underlying the Class B.  Class B airspace is the airspace surrounding the nations largest airports and there are a number of restrictions and requirements that must be met before entering this airspace.  Restrictions designed to help separate aircraft, large and small, in busy terminal areas.

One of the best ways I know to illustrate the general shape of Class B airspace is to picture an upside down wedding cake.  Class B airspace is narrow in the middle and reaches the ground in the immediate vicinity of the airport.  The next layer extends farther from the airport, but does not reach the surface.  There are typically multiple layers that look generally like an upside down wedding cake.


The airport at San Jose is not inside Class B, but rather sits underneath one of the layers of Class B airspace surrounding nearby San Francisco.  According to FAR 91.117, the maximum speed while operating in the airspace underlying Class B is 200 knots, significantly slower than the 250 knot climb typically achieved by an airliner.  It's unusual for airline pilots to find themselves in the airspace underlying the Class B because the shape and design of the airspace is such that airliners rarely exit the Class B airspace if they are landing at the primary airport...which they almost always are.  San Jose is an unusual exception.

Take a look at the diagram below.  The San Francisco International Airport is located in the top left quadrant of the picture with San Jose to the southeast.  According to this chart, the bottom of the Class B airspace over SJC begins at 8,000 feet and extends approximately 5 miles south of the airport.  As a result, when departing San Jose in the direction my flight was cleared, a pilot must fly no faster than 200 knots until climbing above 8,000 feet or traveling more than 5 miles south of the San Jose airport.


The overcast layer of clouds over the airport was less than 2,000 feet thick, so with a climb rate of nearly 5,000 feet per minute, it wasn't long before we were out on top of the clouds which were just now becoming illuminated by the morning sun.  The sun coming up over the mountains to the east created a bright orange glow at the horizon fading to a deep blue sky.  We accelerated to 200 knots, then as we passed 1.8 DME from the SJC VOR, the flight director commanded a 30 degree right bank to intercept the outbound radial of the OAK VOR.  (A fellow pilot sitting on the cockpit jumpseat snapped the picture below.)

In the turn, climbing out on top of the clouds on the SJC9 departure.
We were about half way through the turn when the jet that took off behind us checked in with departure control. They were climbing through 2,500 feet on the same departure we were flying and had the same clearance restriction of 5,000 feet.  It was at that time that the departure controller asked what seemed like an odd question.  "836, do you guys have a problem?"  I glanced over at the Captain and saw that he was looking at me with the same puzzled look I imagine I was sharing with him.  "What on earth is he talking about" I said.

Normally when a pilot gets a question like this, its because he's doing something wrong.  Before answering, I glanced at the departure procedure that was clipped to my yoke and confirmed we were on the correct flight path.  I had checked the DME using raw data instead of relying solely on the FMS to command our initial turn, so I knew we had turned at the right point.  We were passing 4 for 5,000 feet, so I knew we had not violated an altitude restriction and we hadn't flown through the Oakland VOR radial.  What had I missed?  I glanced at our clearance, confirming we were in fact flying the correct procedure as I pressed the push-to-talk button and responded to the controller.

I honestly can't remember my exact words, but I can tell you that it's important to choose your words carefully.  If we had made some error, the last thing I wanted to do was make a comment that put the controller on the defense.  Poking this bear in the face didn't seem like a good idea.  The controller responded that we seemed to be climbing slowly and that he thought we might have a problem.  Climbing slowly?  We were reducing our rate of climb to level off at 5,000 feet, but we had been climbing at nearly 5,000 feet per minute!  What on earth was he getting at?  Then it occurred to me that he might be referring to our speed, not our rate of climb.  

I don't know this for a fact, but I suspect the jet that took off behind us accelerated to 250 knots after takeoff.  I also assume that it was not my speed or rate of climb that initially caught the controllers attention, but rather an impending issue with required spacing as the jet behind us began to crawl up our tail pipe.  None of this occurred to me at the time, but in hind sight, it's a plausible explanation to an odd question.

Under the impression that speed was the issue, I responded that we were complying with the 200 knot restriction and that we would accelerate once we were above 8,000 feet or 5 miles south of the airport.  I remember being a little annoyed.  Doesn't everyone comply with the speed restriction?  The  controller seemed content with my explanation, but I noticed a slight level of irritation in his voice.  

This isn't the first time I've been questioned about my speed in the airspace underlying the Class B and it isn't the first time I've gotten the impression that a controller wished we hadn't obeyed the restriction.  Air Traffic Controllers do not have the authority to delete the speed restriction, but sometimes it seems to be as much a thorn in their side as it is in ours.  I encounter this on a regular basis when descending into the Dallas, Ft. Worth International Airport.  When approaching the airport from the north and landing to the south, we are often given a clearance to descend through the bottom of the Class B airspace.  The DFW approach controllers are adept at warning that we are about to do this, but they usually say something like "speed at your discretion."  Again, they can't omit the speed restriction, but the verbiage used seems to indicate a preference that we don't slow. 

I conducted a small and informal poll of friends and colleagues on this issue and received responses from both pilots and controllers.  The  consensus from every pilot was that they always slow for the restriction...as long as they are aware of it...which admittedly isn't always the case.  It is often difficult to know if you have exited the Class B since the charts typically used by instrument rated pilots do not depict different types of airspace.  For the record, the one in San Jose is well known and clear warnings are issued to pilots operating there. 

The response I got from controllers didn't necessarily surprise me, but it wasn't exactly what I expected either.  In most cases, they sternly reiterated that FAR 91.117 must be complied with.  It's the law and they are expecting us to comply with the restriction.  Most of all, an Air Traffic Controller needs to know our speed and for planning purposes, they need to know when we are going to speed up or slow down.  If we slow unexpectedly or fly any unexpected speed, we could easily throw a wrench into a complicated operation.

As a side note, although it is quite simple for controllers to accurately estimate our speed, I didn't speak to anyone who had ever heard of a pilot being violated for exceeding the limit.  But that's no excuse not to comply.

I think I was correct about one thing...slowing to 200 knots seems as much a pain for them as it is for us.  I suspect they don't like the rule any more than we do, but we ARE expected to comply.  Furthermore, the rule is in place for safety reasons and is intended to help separate aircraft operating at significantly different levels of performance.

At any rate, it's a good learning point.  Departing SJC, pilots tune their radios to the SJC VOR to signal the initial turn, then they are tuned into the Oakland VOR to intercept the outbound radial as commanded by the procedure.  But the Class B is defined by distance from the San Francisco VOR, which neither pilot would normally have tuned in.  It's all very confusing and provides ample opportunity for a mistake.

Be careful out there folks...and remember to fill out your ASAP reports!






1 comment:

  1. Good post! At SJC we ALWAYS nail that 200kt restriction, and that's the ONLY place we ever bother with it! A rare, rare case, but it's out there, lurking.

    I always cringe when a controller says, "Say speed." Or "Say altitude." We always look at each other with deer-in-headlights before answering VERY CAREFULLY!

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