Thursday, October 29, 2009

Automation-Induced Complacency

Image shamelessly stolen from NASA ASRS Callback #315

It would seem that you can't conduct an aviation-related blog without commenting on the saga of the peripatetic Northwest Flight 188. You know - the one where the flight crew reportedly went "Heads-Down-and-Locked" over their personal laptops while 'George' flew the airplane past the intended destination (KMSP) at FL370 and on for another 150 miles into the wilds of darkest Wisconsin. It was the Mother of all LOSA (Loss of Situational Awareness) incidents.

Now it's reported that the FAA has issued an emergency revocation order for the certificates of the Captain and First Officer involved. They can appeal the order to the NTSB but based on the circumstances reported in the press their prospects of continued employment as professional aviators appear bleak. Perhaps that's as it should be. It is certainly easy to imagine ways in which their inattention to duty could have led to catastrophe. But at the same time, I'd suggest that to a degree they were set up.

Based on what's been revealed to date, it looks like this flight crew fell victim to Automation-Induced Complacency. And this is not in any way a new problem. Consider the following quote:

"Another problem concerns the new automatic systems which are coming into service with newer aircraft and being added to older aircraft. Flightcrews become more reliant upon the functioning of sophisticated avionics systems, and their associated automation, to fly the airplane. This is increasingly so as the reliability of such equipment improves. Basic control of the aircraft and supervision of the flight's progress by instrument indications diminish as other more pressing tasks in the cockpit attract attention because of the overreliance on such automatic equipment.

Pilot's testimony indicated that dependence on the reliability and capability of the autopilot is actually greater than anticipated in its early design and its certification. This is particularly true in the cruise phase of flight....

In any event, good pilot practices and company training dictate that one pilot will monitor the progress of the aircraft at all times and under all circumstances."[emphasis added]

Those words come from an NTSB report dated 14 June 1973. The subject is the crash, on the preceding 29 December, of Eastern Airlines Flight 401 in the Florida Everglades. That was the L-1011 aboard which the entire crew was busy troubleshooting an indicator light problem while the airplane - with the autopilot inadvertantly disengaged - spiralled slowly down into the swamp.

And here we are, 36 years later, with another crew allowing themselves to be distracted to the point where no one was flying the airplane! Fortunately, this time nobody died.

"During the long ages between dawn and sunrise, I'm thankful we didn't make the Spirit of St. Louis a stable plane. The very instability which makes it difficult to fly blind or hold an accurate course at night now guards me against excessive errors. It's again a case of the plane and me compensating for each other."
-- Charles A. Lindbergh, "The Spirit of St. Louis"

Flying in the Lone Eagle's day was the polar opposite of today. The problems revolved around task saturation, i.e., there was too much to do. But aviators like Lindbergh and Doolittle and Rickenbacker nonetheless excelled. It was an environment where human beings could, with training, do well. Yet, as aviation matured, new capabilities of pilot and aircraft were needed. Necessity brought forth the autopilot.

"I pay those guys to fly, so let them fly. I'll be damned if I'll pay them to just sit there."
-- reportedly, Eddie Rickenbacker, CEO Eastern Airlines. Eastern aircraft were some of the last to be equipped with autopilots, his pilots saying if it wasn't in Captain Eddie's SPAD he won't buy it. Quoted in 'Human Factors in Multi-Crew Flight Operations' by Orlady & Orlady.

In spite of Capt. Eddie's resistance, flight systems automation has become ubiquitous and now it looks like problems are arising from crews having not enough to do. The terms in current vogue for the flight crew are PF and PM - that's Pilot Flying and Pilot Monitoring. But for long stretches in cruise there is precious little flying for the PF to do, and the PM is probably, like all humans, rather poor at monitoring.

In a 2002 paper entitled Enhancing Flight-crew Monitoring Skills Can Increase Flight Safety, Capts. Robert Sumwalt & Ronald Thomas and NASA's Dr. Key Dismukes point out that:

"...although monitoring may seem intuitive and easy, in reality, continuous and effective monitoring is not natural. In fact, it is most natural to do things as you think of them, instead of delaying them until later. However...an effective monitoring strategy involves sometimes delaying some tasks until less vulnerable periods. It is also not natural to stop doing something in the middle of the task to scan instruments (monitor). Instead, people prefer to complete the task before stopping. However, effective monitoring requires a more-or-less constant scan of instruments."

And, quoting an earlier Air Transport Assn. Automation Sub-Committee paper:

"...serious errors do not occur frequently which can lead to boredom and complacency. 'A low probability, high-criticality error is exactly the one that must be caught and corrected.'" [emphasis added]

And so we have this highly experienced flight crew on NWA188 whiling away the hours from KSAN to KMSP with 'George' doing all the work. Ostensibly, of course, they are "monitoring systems" but you can only devote so much attention to static displays and creeping moving maps. So, being human and fallible, they turn their attention to "more pressing matters" -- like the arcane new pilot scheduling software. And the share of their attention devoted to "monitoring" their progress through the night sky falls to...zero. It's just unlikely enough to be the truth.

I think of the times I've been humming along over eastern Pennsylvania with 'George' in control of N631S and the GPS in control of 'George' and me, both the PF and the PM, with no flying to do and not a lot to monitor. If there were a distraction available, I might be vulnerable. So, while I can't excuse the guys up front on NWA188, I can see how they got in trouble.

The airlines may want to look into ways to keep the flight crew engaged with the airplane during extended low-workload periods. There is, for example, the concept of Adaptive Automation which uses novel approaches to task allocation and task partitioning to be responsive to changes in workload and operator behavior. The system could deliberately cede tasks to the pilots during low-workload periods simply to maintain a minimum level of operator involvement.

For my part, I think I'll just continue to keep Rule 1 in mind: Always fly the airplane!

Sunday, October 25, 2009

Post #100

As it happens, I put up the first post on this blog eight months ago - 25 February 09. This being the 100th post, I seem to have been holding forth 12.5 times each month.

According to data collected by statcounter.com, there have been roughly 14 visits/day over the last two weeks. A sizable percentage of the visitors are responding to search-engine hits (mostly Google).

A few posts in the archive seem to be "best sellers", as they keep getting Google-inspired visits. In order of "popularity", these include:

Statcounter.com also provides the geographic location and IP address of visitors. You get to know the folks who come back more than a few times. I seem to have "fans" in (among other places) South Bend, IN (someone who works the midnight shift, judging from the times he/she visits), Stillwater, OK (possibly two folks, one of whom logs on from OSU), Overland Park, KS and Hammond, IN. To these folks and others who have taken the time to stop by and read the blog, I'd like to say, "Thanks!"

Saturday, October 24, 2009

About Last Night...

I took note previously of the TFR attendant to the President's visit to Stamford, CT. For my departure from KBDR (which was in the area covered by the "outer ring" TFR but outside the core "no-fly" area), the whole thing was pretty much transparent to the IFR user. The only change from usual practices occurred when Clearance Delivery asked that I give them a "heads-up" call five minutes before I was ready to taxi so that they could coordinate the departure. That's not normally needed.

After departure everything proceeded as usual. I did hear one conversation wherein ATC was helping a pilot who'd intended to go to KHPN figure out where he wanted to land to wait for that airport to open to General Aviation traffic. (White Plains was in the area of the "core" TFR.)

With the approach of the cold front (something that seems to be happening on a seven-day cycle timed to provide the week's most interesting weather on Friday evening), I got to fly through the schmoo over most of eastern Pennsylvania and on down to Baltimore.

Just past KBWI at 6000 feet, N631S and I flew through a rather small but fairly intense piece of weather isolated from the bulk of the stuff, with about three minutes of moderate precip and light-to-moderate turbulence. Scanning the dials, I noticed a loss of air speed. Glancing over at the manifold pressure gage, I saw that it was down to about 18 inches instead of the 22 or so I'd expect at that altitude. Aha! Carburetor icing! The carb inlet air temp gage was just below the top of the yellow arc at about 4 degrees C. I immediately applied full carb heat. The engine went a little bit rough and there was one "hiccup" as, presumably, a piece of ice broke loose and passed through the engine as a slug of water. But in less than a minute the manifold pressure was back to expected levels and the aircraft accelerated to the speed I'd been getting before. I reduced the carb heat to just the amount needed to keep the gage out of the yellow and had no further issue.

The good news is that the area right around home had good VMC, so the visual approach into KVKX was on offer. As a minor complication to end my day, the Potomac Approach controller needed to keep me high until quite close in and I wound up with a "slam-dunk" approach. From 2000 feet and 2+ miles out, I wasn't able to get down for a normal approach to landing so I wound up executing a go-around. Good practice.

Friday, October 23, 2009

Hail to the Chief

The President is coming to town for his own political purposes, and bringing with him his traveling circus of Temporary Flight Restrictions. From 2030Z to 0010Z tonight there are a pair of TFR's centered on a point on the Carmel (CMK) 189 radial at 14.2nm. I believe that's one of the hotels in Stamford where the party is going to be.

The folks in charge of security theater have promulgated a NOTAM in typically opaque language warning off all of us aviators. Fortunately our good friends at the FAA have provided an explanatory web site that provides guidance we can actually understand. They even include graphics:

As you can see, Bridgeport (KBDR) is outside the inner TFR (which is the real "no fly zone") and within the outer ring, where operations are possible as long as you are on an active flight plan and in touch with ATC.

If I depart, as planned, shortly after 21Z, I will have to be sure to get a turn to the north right away - which Approach Control usually issues to me anyway. This doesn't really take me any further out of my way than I'm accustomed to. It's just that the penalties for messing up are rather more severe.

Oh, yes, the weather. The forecast is for light rain showers in the area on arrival around 00Z. There may be some issues with low ceilings...I've got Manassas for an alternate.

Wednesday, October 21, 2009

Stupid Pilot Trick

A video clip that showed up recently on YouTube has been generating quite a bit of commentary on the aviation internet forums I frequent. Recorded by a passenger, it shows an unintended encounter with IMC and a resulting really close encounter with the local trees and bushes - to the point where the aircraft sustains impact damage but manages to return safely to the airport. The consensus of the pilot community seems to be that this pilot displays monumentally poor judgment. If you haven't yet seen this, here it is. Have a look (about 3 minutes running time).

I don't take issue with the position that the behavior shown here is about as bad as it can get. It is astounding that the flight shown didn't terminate with a smoking hole on the side of the mountain. What does give me pause is an underlying current in the commentary implying, "Hey, I'd never do that." Not smugness, just a feeling of disbelief that the observer could at any time even approach that level of stupidity.

To anyone who just can't conceive of ever being the central player in such a misadventure, I have a book I'd like to commend to you.

In Darker Shades of Blue: The Rogue Pilot Tony Kern explores the phenomenon of the aviator who inexplicably throws caution to the winds and behaves in ways that seem to invite fatal mishap. He explores many case studies and delves into the root causes of the FAA's familiar five Hazardous Attitudes (found in AC60-22 on Aeronautical Decision Making, available at: Link 1 and Link2). I won't try to summarize Dr. Kern's work here (please find and read the book). But at the end he concludes that, on any given day and for any given flight, every one of us harbors the potential to become that rogue pilot who abandons discipline with catastrophic results. Awareness of this potential is our sharpest tool in avoiding the terrible consequences of such behavior.

So I return to the Bonanza pilot seen in the linked video, not to condone him (he surely will - and should - face consequences for his actions, but for now they won't be fatal to anyone), but to acknowledge that there, but for the exercise of constant vigilance, go even the best of us.

Saturday, October 17, 2009

The Balloon Goes Up

Twice each day, at 00Z and 12Z, weather balloons are released at a multitude of locations around the globe. As they rise, they are tracked by radar to obtain data on winds aloft. Each balloon carries a sensor package (called a "radiosonde") that records air data and transmits it to the ground.

At NOAA/ESRL Radiosonde Database Access you can access the archived "RaOb" data. The data can be had in various output formats including a very nice Skew-T Plot. ("ESRL" stands for NOAA Earth System Research Laboratory.)

Here are the Skew-T plots for 00Z last night derived from the 00Z soundings at Brookhaven, NY (OKX, on Long Island) and Sterling, VA (at IAD, Dulles Airport):

The plot for OKX shows the atmosphere as it stood a couple hours after I'd have left KBDR (if I hadn't decided that AmTrak was a better idea). The IAD plot shows what I'd have found on arrival at VKX. On both plots the red data curve is temperature and the blue one is dew point. The isotherms (lines of constant temperature) are tilted 45 degrees to the right (hence the term Skew-T) and the height scale is calibrated in millibars. The 850 Mb pressure level is about 5,000 feet altitude and the 700 Mb level is about 10,000 feet. (The stuff on the right side is a hodograph giving wind speed and direction vs. pressure level.)

Look at the OKX sounding. You can see that the temperature and dew point plots merge at about 900 Mb (around 3,500 feet). That makes it very likely that there would have been clouds at that level. The curves hit the 0 degree Celsius isotherm at about the same height. That says those clouds would probably have ice in them.

A look at the IAD sounding shows a slightly warmer lower atmosphere. The temperature and dew point curves don't reach the freezing point until about 850 Mb (5,000 feet). But they are really close together from a very low altitude. That says to me that low ceilings are a distinct possibility.

These two plots leave me convinced that if I'd attempted to fly from KBDR to VKX last evening I'd have probably gotten involved with serious icing. And if that's not enough, I can show you the METAR for Andrews AFB (four miles away from VKX) at about the time I'd have arrived:
KADW 162347Z AUTO 36010KT 7SM R01R/5000V5500FT R01L/4500V5500FT +RA OVC005 05/05 A2995 RMK AO2 UPB2315E2346RAB2258E2315B2346DZE2311 SLP147 $
If I'd somehow managed to cope with the icing I'd have arrived to find heavy rain and a 500 foot overcast. Probably a missed approach and a diversion to Manassas (KHEF). Here's the KHEF weather about an hour later:
KHEF 170055Z AUTO 35007KT 5SM BKN008 OVC014 06/03 A2998 RMK AO1
A bit better. No precip, five miles visibility under an 800 foot ceiling. Still, all in all I'm glad I was on the train.

Incidentally, you can go to Soundings From ESRL/GSD to get forecast Skew-T sounding plots for just about any airport. A very useful weather resource.

Thursday, October 15, 2009

Railroad Weather

It looks like tomorrow night will have a clear case of AmTrak Weather. The combination of moisture and freezing temperatures aloft seem to be dictating a trip to DC at 0 feet AGL.

First, take a look at where the freezing level is going to be:

The map above shows the forecast freezing levels (NAM model, 12Z run) for about the time I'd be wanting to land at VKX. You can see that my normal routing over southeastern New York and down over central New Jersey and eastern Pennsylvania, at 6,000 to 8,000 feet MSL, would have a high icing potential.

Even if I could talk ATC into a routing over JFK and down the New Jersey coast, the northern part of the route would be a problem.

Now add in the moisture. Here's the forecast simulated radar image for the same time period:

That suggests some pretty solid precip returns over the southern parts of the trip. Not a pretty picture.

Finally, let's look at a couple of Terminal Area Forecasts going out to 00Z tomorrow night:

KJFK 151737Z 1518/1624 05016G22KT 4SM -RA BKN015 OVC025
    FM152000 05017G23KT 4SM -RA BR SCT009 OVC012
    TEMPO 1521/1524 2SM RA BR OVC009
    FM160000 04020G27KT 2SM -RA BR OVC008
    TEMPO 1604/1608 4SM -RA BR OVC010
    FM160800 02020G28KT 4SM -RA BR OVC012
    FM161300 02017G25KT 4SM -RA BR OVC012

KBWI 151725Z 1518/1624 07012KT 2SM -RA BR BKN008 OVC012
    FM151900 04012G20KT 4SM -RADZ BR SCT004 OVC008
    FM152300 03013G23KT 5SM -RADZ BR FEW002 BKN004 OVC009
    FM160400 02010G18KT 6SM -RA BR OVC003
    FM161300 01010KT 5SM -DZ SCT003 OVC006

KIAD 151725Z 1518/1624 06007KT 3SM -RA BR SCT005 BKN009 OVC015
    FM152100 03010KT 4SM -RADZ BR FEW002 BKN004 OVC009
    FM160200 01007KT 5SM -DZ BR OVC002
    FM161200 36006KT 4SM -DZ BR SCT002 OVC005

In the New York City area at the probable time of departure (say, 21Z), it's looking like gusty winds from the NNE with light rain and mist and a 1200 foot overcast. And for the ETA timeframe (about 23Z to 00Z) Baltimore is forecast to have 5 miles visibility in light drizzle with a 600 foot overcast and Dulles looks to have the same weather with a 500 foot overcast.

The only instrument approach into VKX, the RNAV 6, has a Minimum Descent Altitude of 680 feet MSL, so even if I could contrive to make the flight without icing up N631S, there is an excellent chance I'd have to go missed approach at VKX and wind up at Manassas.

I shall look at the weather again in the morning, but as of now it looks to add up to a nice train trip and a late (but safe) arrival at home.

Wednesday, October 14, 2009

Vacuum Pump Failure (cont'd)

Two days ago I put up a post concerning the (really quite benign) circumstances surrounding the failure of N631S's vacuum pump and the subsequent installation of a new one. But perhaps the subject is worth a little more discussion.

It's an element of "common knowledge" in General Aviation that dry-vane vacuum pumps fail after around 500 hours in service. Monday's failure occurred at 576.6 hours. I had the predecessor component replaced prophylactically at 573 hours. So the question arises naturally: why did I not replace the unit that failed when it reached 500 hours in service a few months ago? Well, it's all Mike Busch's fault.

I've been a fan of Mike and his approach to aircraft maintenance since I ran into his "Savvy Aviator" columns on the AvWeb site. I've taken his seminar (probably the highest-ROI dollars and hours I've spent as an aircraft owner) and I read his articles first when the Cessna Pilots Association magazine shows up each month.

One particular series of three columns that Mike wrote in 2007 on the topic of Reliability Centered Maintenance is on point for the present conversation.

In these columns, Mike uses real world research and analysis to deprecate the time-worn concept of TBO. I can't summarize his work in a paragraph or two (please, go read the columns!) but I think it's fair to say that he makes a good case for maintaining "on condition" where tools exist to evaluate condition and where the relationship between failure probability vs. time and the consequences of failure can be well understood.

For example, we used to run an engine for 2,000 hours and then pull it off the airframe and send it out for overhaul. Now, we carefully examine oil filter media and do spectrometric oil analysis at each oil change. As long as we don't find alarming deposits in the filter, nor see unsettling trends in the oil analysis reports, we keep on running the engine.

We used to rework cylinders if the compression test result fell below some arbitrary value. Now we do a much "smarter" compression test and we rely on borescope inspection more heavily in judging whether a jug is actually in trouble.

But how should we deal with components that offer no good way to evaluate condition? Until recently, vacuum pumps fell into that category.

(Note: The pump that was just installed in N631S has an inspection port. It is now possible to open this port, align a vane with the opening, and insert a probe to measure the amount of wear the pump vanes have accumulated. The manufacturer recommends an initial inspection at 500 hours and subsequent inspections at 100 hour intervals, and provides a "go/no go" limit for wear that dictates when the pump should be removed from service. Older pumps lacked this feature.)
Inside the pump (See photo at left from Sacramento Sky Ranch Inc.), a carbon rotor spins within the ellipsoidal cavity. The carbon vanes ride in grooves in the rotor and are thrust outward by centrifugal force, against the cavity wall. The vanes push the air around, and of course over time they wear. Eventually they wear to the point that they come adrift, and the pump fails - abruptly and catastrophically. Lots of them fail at around 500 hours. Lots more will go for 700 or 800 or even 1,000 hours. Until the advent of the latest pump design, it has been infeasible to evaluate the condition of the pump in service, so the choices available have been:
  • Replace the pump on a preventive basis at or near 500 hours in service.
  • Run to failure, with the understanding that an in flight failure will have consequences that must be managed.

A vacuum system failure can be insidious and deadly. For example, this NTSB report describes a fatal 2004 accident where a vacuum pump failure killed an unprepared pilot. The fatal Carnahan accident in 2000, is well known and was probably central to Parker-Hannifin's decision to withdraw from the aircraft vacuum pump business. The FAA, for it's part, has published pamphlet P-8740-52 titled "Silent Emergency: Pneumatic System Failure", describing the insidious nature of vacuum failures and recommending protective measures. Rapco, the current vacuum pump manufacturer, recommends that those who install their products provide this pamphlet to the aircraft owner and enter the fact that they have done so in the airplane's maintenance records.

Back, then, to the question: why didn't I replace N631S's vacuum pump at 500 hours in service? After all, I had replaced the previous unit based on time in service. The answer is that in the intervening time I had absorbed Mike Busch's teaching on Reliability Centered Maintenance and had adopted the philosophy in maintaining N631S. In the case of the vacuum pump, I could not maintain "on condition", so I chose to develop a plan for managing the consequences of failure and then to consciously adopt a "run-to-failure" strategy.

The problem is two-fold. First you have to plan to recognize the failure and second, you have to plan to deal with the failure. For the first part, I had the Precise Flight low-vacuum annunciator installed - and it worked. When the pump failed, the light lit and I was aware of the problem in a very few seconds.

I was fortunate that the failure occurred in good VMC weather. But if it had occurred in IMC, I could have dealt with the failure using two resources that are fully independent of the vacuum system. First, the STEC System 50 autopilot bases its control of the aircraft on the output of the turn coordinator, an electrical gyro. (Those who fly with an autopilot that references the pneumatically driven DG or HSI need a different strategy.) Second, the GPS, backed up by the compass, provides the course guidance needed to get out of trouble. Therefore, I had confidence that I would recognize and have the ability to manage a pump failure in any set of flight conditions.

A vacuum pump can fail at any time, so this plan for managing failure of the pump remains in effect. However, I expect that when the new pump's 500th hour rolls around I will be exercising the new inspection capability to establish its condition and decide whether it needs replacement.

Monday, October 12, 2009

If You Must Have a Failure...

This morning I departed VKX for the weekly trip up to Connecticut - twice. The first time, N631S's wheels left the runway at 1155Z and we were back on the ground by 1220Z. The entire flight looked (courtesy of FlightAware.com) like this:

I departed VFR from runway 6 and turned to the south from the left downwind. Staying below the 1500 foot MSL floor of the Washington Class B airspace, I contacted Potomac Approach. Once radar identified, I was cleared to turn to a 120 heading and to climb to and maintain 5000 feet. I was handed off to another sector and cleared to turn left toward OTT and thence to POLLA, my first enroute fix.

That's when the vacuum pump failed.

In May 2005, when N631S's avionics were upgraded, I had the shop install a Precise Flight Vacuum Failure Warning Indicator. This morning, it earned its place on the panel as it shone in all its amber glory announcing "LOW VAC"!

I quickly cross-checked with the suction gage. It wasn't low, it was on zero. Zip, nada, no vacuum at all.

The vacuum pump had failed abruptly and completely. Meanwhile, the associated gyros were still spinning but that wouldn't continue for long. The good news was that I was in excellent VMC. So, I transmitted, "Potomac Approach, Skylane 631 Sierra needs to return to VKX. We've had a vacuum pump failure. It is not an emergency." The immediate response was, "31 Sierra, stand by," followed in about half a minute by, "Skylane 631 Sierra, descend and maintain 2000, turn left heading of 260. You are cleared present position to VKX via radar vectors."

The rest of the flight was a straightforward visual return to Potomac Airfield. Although I will admit that watching the vacuum driven attitude indicator roll over and die was disconcerting. It made clear the importance of covering failed instruments to avoid distraction in IMC.

Back on the ground, I called Phil McClanahan, A&P mechanic par excellance. He listened to my tale and said, "I think I've got one of them in my hangar." So I opened up my hangar again, removed my automobile, and pulled N631S back inside. As I was about to start removing the upper cowl, Phil showed up with a toolbox and a new Rapco RA216CW dry-vane vacuum pump.

In September of 2004, when I took over the care and flying of N631S, I was not comfortable with the fact that the vacuum pump had accumulated 573 hours. There was no warning annunciator, no backup, and a failure in IMC could be most inconvenient. So I asked the folks at Lindner Aviation in Keokuk, IA (who had taken care of the airplane for the previous owners) to put in a new pump. The tach showed 3245.0 hours.

This morning the pump failed at about 3821.6 hours, having lasted in service for 576.6 hours.

It took Phil about 45 minutes to remove the failed pump, install the new pump, and examine the filter for any evidence of contamination. We ran up the airplane and got "ops normal" from the vacuum system and the instruments, buttoned up the cowl, and were, as it's said, good to go.

OK, there was a failure. But that was the extent of the bad news. The good news included:

  • It was certainly not a premature failure. The pump had given good service.
  • It was good that it failed in day VMC rather than at night in the clag (as would have been the case if it had gone "tango uniform" one hour sooner - on Friday night.
  • It was reassuring to see the Precise Flight annunciator system perform its intended function.
  • It was good that Phil was available and that he had a new pump to install.
I hope (not expect) that all of my equipment failures are similar to this one.

I took off for KBDR the second time at 1445Z and had an uneventful 1.9 hour flight.

Friday, October 9, 2009

Changes at KBDR (cont'd)

About five months ago (May 15th, to be exact) I posted about the demolition of the old passenger terminal at KBDR. It was going to make way for a new Hangar/Executive Terminal being built under the aegis of Volo Aviation.

Since then, most of the progress has been below grade. But in the last week, steel has been going up.

It will be interesting to see the design of the building as it approaches completion. I hope it's reasonably attractive.

By the way, tonight's trip from KBDR down to VKX was uneventful but tediously long. Headwinds of nearly 60 knots over eastern Pennsylvania led to a 3.1 hour flight, despite several helpful shortcuts offered by ATC. Oh well, I'm here.

Wednesday, October 7, 2009

The Usual Routing

The clever folks at FlightAware.com keep enhancing their product. Of late they've added useful information to the track image that they make available for each monitored flight. For example, here's what they display for N631S's flight last Friday evening from KBDR in Connecticut to VKX in the DC area:

The solid green line is the actual track of the aircraft, while the intermittent blue line is supposed to be the track of the original clearance (there are some issues at the south end). The differences in the two lines are the result of en route changes to the clearance.

Here in the busy northeast, the Air Traffic Control system is rather inflexible regarding IFR routing assignments. Unlike the great spaces of the midwest, where "Cleared as filed" is commonly heard, in these parts it doesn't matter what you file - you get the "preferred" route.

I am trainable. I now routinely file for the route that I know I'm going to get anyway: from KBDR direct SAX V249 SBJ V30 ETX V39 LRP V93 BAL direct VKX. In plain English, that says: departing Bridgeport, expect radar vectors to Sparta, NJ; then join airway V249 southbound to Solberg, NJ. From there follow airway V30 west to the East Texas VOR near Allentown, PA and take a left on airway V39 to Lancaster, PA. Then follow airway V93 to Baltimore, MD and thence direct to destination, Potomac Airfield (a.k.a. VKX).

I have that route programmed in the GNS-530W because I know I am very likely to be cleared for it. But I also know that there will be some en route changes both for the convenience of the Air Traffic Control (ATC) system and to send me expeditiously on my way.

I expect on a typical trip, for example, to be directed to the north as I depart Bridgeport. This ensures that I will pass to the north of the New York Class B airspace when I am eventually allowed to turn to the west. Also, I am usually cleared quickly to climb to 6,000 feet MSL.

The controller soon turns me to the west, toward the Carmel VOR (CMK), clears me to 7,000 feet and hands me off to the control sector responsible for the airspace north of White Plains (KHPN). This gets me above their arrivals from the north. Approaching the Hudson River, I am usually cleared up to 8,000 feet MSL and sent "direct Sparta". As I tell the auto-pilot to take me to SAX I am handed off to the Newark (KEWR) approach sector. I'm now above their southbound arrivals and often see the Boeings and Airbii passing majestically beneath my flight path.

I turn to the south at SAX, joining V249 toward Solberg...but it's rare for me to get there. I suspect that the Newark controller is on the land line with Allentown Approach, arranging the handoff. They agree that I can have a short-cut, turning a bit to the southwest to join V30 at the LANNA intersection.

Newark tells me, "Skylane 31 Sierra, proceed direct LANNA," and then a minute later, "31 Sierra contact Allentown Approach on 124.45." I respond, "124.45 for 31 Sierra...thanks and so long." I make the frequency change, listen for ten seconds to be certain I won't block someone's transmission, and then check in with Allentown.

Allentown is usually far less busy than the New York sectors (unless the weather is boisterous. See, for example, this post.) I join V30 at LANNA and motor along for a few minutes until I'm approaching a fix called BOPLY. At this point, V30 veers a bit to the north, which is not productive. But experience has taught me that if I ask nicely I will be cleared to a fix on V39 called FLOAT. It's south of East Texas and just north of the Reading, PA airport. A nice little short-cut.

Waiting for a quiet moment, I key the mike to say, "Allentown Approach, Skylane 631 Sierra, request." I hear, "31 Sierra, go ahead," and say "Any chance of direct FLOAT along here for 31 Sierra?" With no hesitation, I will normally get, "Skylane 31 Sierra, proceed direct FLOAT, join Victor 39, resume own navigation." Nice.

Nearing FLOAT, Allentown gets the next hand-off and gives me a frequency to contact Harrisburg Approach. I join V39 at Reading and turn south toward Lancaster. Harrisburg Approach is already coordinating my hand-off to Potomac Approach and my entry into the Washington, DC Special Flight Rules Area (SFRA). (On a busy night, I've been given delaying vectors, waiting for Potomac Approach to agree to my entry into their domain.) But on a typical trip, I may hear, "Skylane 31 Sierra, after Lancaster proceed direct Baltimore." Another small shortcut, and every bit helps.

Approaching the Susquehanna River, I will be directed by Harrisburg Approach to descend to and maintain an altitude of 6,000 feet. I push the nose over and accelerate to 140 knots indicated airspeed. N631S descends nicely and the speed pays me back, in part, for time lost in the climb over Connecticut.

Crossing the river I get from Harrisburg the first Potomac Approach frequency. "Thanks and so long," and I check in with Potomac.

I'm at 6,000 feet MSL which is where they want me to cross over the Baltimore-Washington International (KBWI) airport. And usually, the controller in this first Potomac Approach sector will tell me, "31 Sierra, after Baltimore proceed direct Nottingham, then direct to Potomac Airfield."

I knew that. My clearance, which is for Baltimore thence direct VKX, is really not feasible because it would take me right over Andrews AFB. Not going to happen. So I am rerouted, south from Baltimore to the Nottingham (OTT) VOR and only then direct to VKX. It adds about 10 miles to my route and avoids Andrews.

I've tried filing for OTT after BAL. Nope. Every time the ATC computer spits out "...BAL direct VKX", and every time, Potomac Approach has to reroute me to OTT. Go figure.

I cross directly over KBWI and head down to Nottingham. About 10 miles south of KBWI I will be cleared down to 4,000 feet and often, before reaching that altitude, cleared further down to 3,000 feet. If the weather is fine, the controller tells me, "Expect the visual approach at Potomac." And then, "31 Sierra depart Nottingham on heading 250." The controller is going to take me to the southwest, past VKX, and then turn me toward the airport.

Sure enough, I soon hear, "31 Sierra, descend to 2,000 and proceed direct VKX," and I turn to the northeast and look for the airport. On a good night I'll pick up the beacon fairly quickly and advise the controller that I have the field in sight. I cancel my IFR flight plan and get transferred to the local advisory frequency.

Now it's just a question of keeping the airfield in sight, making the appropriate traffic calls on the local frequency, and setting up 631S for landing.

It's good to be home.

Saturday, October 3, 2009

Uphill Flight

Last night's flight down to VKX from KBDR was long! 3.0 hours long. The headwind from the south-southwest was ferocious - over 50 knots at 8000 feet and "only" about 40 knots at 6000 feet. For most of the trip N631S was delivering a true air speed of about 137 knots, but the ground speed was frequently less than 100 knots.

The good news is that the weather situation was just as forecast (see this post).

The photo shows the screen of the GPSmap 396 approaching Lancaster, PA, and the point is that the weather seen off to the west was about as close as it got. In and out of the layered clouds, as expected, but no precipitation.

I was happy to be done for the day when I landed at Potomac Airfield. Courtesy of our friends at Flight Aware, here's the track:

Thursday, October 1, 2009

A Change in the Weather

Summer is over. The temperature at KBDR at 12Z this morning was a brisk 7C. And with the change of season we can be a bit more relaxed about convective weather, but will have to start paying close attention to icing potential.

Here is the big picture, as forecast by NCEP for about the time I expect to be arriving at VKX tomorrow evening (00Z Saturday):

It looks like I can expect good weather for my departure from Connecticut, then likely some clouds to fly through in Eastern Pennsylvania (that assumes the usual routing west to Allentown then south over Lancaster and Baltimore). Then I'll be getting home about as the leading edge of the weather reaches the DC area.

Now I'm very interested in where the freezing level is going to be.

The chart at left, from Aviation Weather Center's Winds and Temps page, shows the forecast for the isotherms at 9000 feet MSL at 00Z tomorrow evening. It's comforting to note that the 0 C line is well to the north. (I expect to be at 6000 or 8000 MSL for most of the trip.)

Finally, below is a segment of the simulated radar graphic for 00Z tomorrow derived from the output of the NAM model run at 12Z today. That model tells me to anticipate a little very light precipitation over northeastern PA, and that's about it.

N631S and I are going to have some pretty strong headwinds (about 30 knots out of the southwest ahead of the cold front), so it's going to be a long trip. FltPlan.com is calculating 2 hours + 38 minutes enroute. If I can arrange to get out of KBDR about 21Z I can expect to get to VKX about 2340Z.

It should be a good trip.