- Circuit breakers are installed on aircraft to protect wiring. [Emphasis added] When current flow in a system exceeds a predetermined value for a period of time, the circuit breaker activates, or “trips,” to stop current flow through that system by breaking the electrical circuit. To use the system after a circuit breaker trips, a pilot must reset that circuit breaker manually. Historically, it has been common practice to reset a circuit breaker on an airplane one time after the breaker trips. ... However, this practice does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of the damage. The aviation industry has begun to recognize the potential hazards of resetting noncritical circuit breakers even once.
- Quoting the FAA's 2004 AC 120-80 on "In-Flight Fires": Crewmembers may create a potentially hazardous situation if they reset a CB without knowing what caused it to trip. A tripped CB should not be reset in flight...unless, in the judgment of the captain, resetting the CB is necessary for the safe completion of the flight. [Emphasis Added]
- [M]any Part 91 pilots and operators have not yet made changes to address current guidance about circuit-breaker resets. ...[M]any general aviation pilots, mechanics, and operators may not have reviewed AC 120-80. ...the guidance contained in manuals provided by general aviation airplane manufacturers often directly conflicts with the guidance contained in AC 120-80. ...general aviation pilots, mechanics, or operators who did review the AC might not have perceived its relevance to their operations.
- The Safety Board concludes that existing guidance in manuals provided by general aviation airplane manufacturers regarding the resetting of circuit breakers often does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of such damage. ...if general aviation pilots, maintenance personnel, and operators had a more thorough understanding of the potential hazards of a reset circuit breaker (as outlined in AC 120-80), they would be less likely to reset a tripped circuit breaker without knowing what caused that circuit breaker to trip. ...the FAA should develop a safety alert for operators (SAFO) informing general aviation pilots and maintenance personnel of the circuit breaker policy contained in AC 120-80. ...the FAA should require that the contents of the SAFO ... be included in initial and required biennial training for general aviation pilots and maintenance personnel.
Thursday, July 30, 2009
Tuesday, July 28, 2009
Saturday, July 25, 2009
Tuesday, July 21, 2009
Saturday, July 18, 2009
The summer afternoon standard-issue convective weather was kicking up its heels over eastern Pennsylvania as I launched from KBDR; wheels off the runway at 2120Z. My IFR clearance was for the usual routing: SAX V249 SBJ V30 ETX V39 LRP V93 BAL Direct, at 8000 feet. I was watching the NEXRAD weather radar picture from XM Weather on the Garmin GPSmap 396 and planning a strategy for working between and around the nastier looking bits.
Before the shortcut to LANNA I'd been headed to SBJ, well clear of the storm cell west of my track heading northeast. Before accepting "Direct LANNA" I'd looked carefully at that and concluded that the resulting track was still going to keep me out of trouble with that one.
At that point I shifted my focus to the cell that shows up south of the airway west of LANNA - that's V30. In the picture above it's partly hidden by the track readout "237" but it was headed in a threatening direction.
Just about then, the New York controller said, "31 Sierra, contact Allentown Approach on 124.45." Before checking in with Allentown I looked at the weather situation. The prudent thing to do would be to continue toward LANNA until clear of the cell to the west, then turn behind it to the west so as to miss the one up ahead. I transmitted, "Allentown Approach, Skylane 631 Sierra, level 8000 with a request." That got me an immediate, "631S, Allentown altimeter 29.75 and what is your request?"
I said, "In about 15 miles 31 Sierra will need direct FJC, then direct ETX to rejoin V39, for weather avoidance." The lady said, "31S that will be approved...you may not need it when you get there."
I settled down to watch the weather evolve and listened as the controller did a masterful job of using her radar weather depiction (Approach Control Radar reportedly has pretty good weather capability) and her complete grasp of what each airplane in her airspace needed to keep the potentially chaotic situation under perfect control. Controllers would say of her, admiringly, that "she had the flick."
The cell I was watching continued to move into my path and just as I was about to key the mike and ask for a diversion the controller transmitted, "Skylane 31 Sierra, cleared direct to the Allentown VOR." I immediately entered Direct FJC into the GPS that was driving N631S and turned away from the storm cell. It was about 2222Z and the situation looked like this:
About halfway to FJC I was wondering when to ask for "direct ETX" when my favorite controller said, "Skylane 31 Sierra, from your present position it looks like a straight shot to East Texas will miss all the heavy precipitation. What do you think?" I figured I'd probably catch just the edges of the moderate precip, but was well past the core of the cell, so I responded, "31 Sierra thinks direct East Texas now will be fine." She said, "31 Sierra, cleared direct East Texas."
I did fly through some moderate rain, and minimal turbulence - no big deal. As I flew toward ETX I continued to be impressed by the lady's work, sending airplanes where their pilots needed to go, advising that some requests for re-routes were a Bad Idea and generally doing a fantastic job at a busy time. And I never heard even the tiniest hint of stress in her voice.
Soon, she said, "Skylane 31 Sierra, contact Harrisburg Approach on (some freq) and have a good evening." I thanked her for her help and said, "Great job!" Minutes later I was out of the precipitation and dealing with clearing skies over Lancaster.
Today, I'm working on tracking down an e-mail address for the manager at Allentown Approach. I want to let them know that the lady on 124.45 at 2200Z last night is one terrific controller.
Wednesday, July 15, 2009
The first item was an oil change, accomplished at the same time that they installed the Cessna seat-stop modification. It being summer, we put in Aeroshell 100W oil, as opposed to the Aeroshell 80W that the engine runs on in cooler weather. I've now been following this routine for about 500 hours and the engine seems to be loving it.
I always have a spectrographic analysis done on a sample of the used oil and it has come back from the lab as normally unremarkable.
The second item was triggered by one of those "hmmm" moments during my run-up a couple of weeks ago before a flight from VKX up to KBDR. After taking the engine RPM up to 1,700 and getting a good magneto check and good propeller pitch cycling, I pulled out the knob for the carburetor heat and...nothing happened. Not too good.
The wonderful Continental O-470U engine that pulls N631S along does have one important idiosyncracy. It is an ice maker that would make the Frigidaire folks proud. The carburetor is mounted on the bottom of the engine and the throttle body stands well off under the crankcase, in a comparatively cool environment. As a result, the carb is prone to the accretion of ice in the venturi section. When that happens it can choke off the flow of combustible stuff into the cylinders and the engine stops running. This can be inconvenient at any altitude greater than about 2 feet AGL. The cure for carburetor icing is to provide a valve that diverts the incoming air flow past the nice hot exhaust plumbing, thus preheating it and making ice accretion unlikely. If the carb heat is not working as designed you are left without a weapon to combat carb icing.
On the morning in question, the sky was clear and (more importantly) the humidity was low (i.e., there was a good spread between temperature and dew point). So I assessed the risk of carb icing as minimal and made the flight to KBDR. On arrival I asked the nice folks at Three Wing to take a look at N631S's carb heat valve.
The valve in question is a squarish plate that rotates open or closed on a shaft turned by a bell crank attached to a cable that is pulled by the control knob in the cockpit. In this case, the fasteners that attach the valve plate to the shaft had sheared. I guess after 32 years and 3,750 hours this kind of thing can happen. Tony at Three Wing opened up the carburetor air-box assembly and re-secured the valve to its shaft.
The last item involved the electric pitch trim control. For a while I had been not liking the feel of the yoke-mounted thumb-switch that actuates the pitch trim. It had developed a "sticky" spot. So I asked Dave at Three Wing to look at it. He agreed that it wasn't right and ought to be replaced.
The reason this matters is that the switch might fail in one of its "ON" positions and cause a runaway trim actuation. If this happens at an awkward time (say, just after takeoff) things can quickly get a bit too interesting.
The bad news is that the manufacturer wants $495 for a new switch! (No, it isn't made out of gold - just priced that way.) So for the time being, I have elected to render the electric trim option INOP and make do with manual trim adjustment. I am on the lookout for a used switch and meanwhile Three Wing pulled the electric trim circuit breaker and made a nice little placard saying "Electric Trim Inop".
Sunday, July 12, 2009
Bob soloed in an Aeronca C3 on floats in 1939. He served his country during WWII in the CPT program and in the USAAF, attaining the rank of Captain. He went on to a rewarding career in business, but always stayed involved in instructing. Last year he received the FAA's Wright Brothers Award for those with over a half-century of contribution to aviation.
My mind does not usually work in verse, but for some reason as I tried to put my feelings about Bob's passing into words this is what came out:
After flecking the clouds with pink and gold hues,
An airfield lies nestled in a valley, under clear blue skies.
The grass strip is home to machines of wood and fabric, wire and dope,
With round engines and spruce props turned by AvGas and the hope
That it won’t quit now – but out there it seems they never do.
Every now and again a new one drones in from the East – there’s always a tiedown
For at least one more, and the guys hangar-flying near the line shack door
Pause and look up as a biplane comes into view above the hill.
The pilot overflies the field, to see what the wind will do, and banks onto the downwind.
He turns base and final, squaring the turns and slipping down to the flare,
Scrubbing off altitude he’d kept in the bank in case the old Continental picked then to tank.
Reacting to the gentle crosswind flow he holds the upwind wings a bit low,
And pulls the stick back, landing in a full-stall. Rolls out, taxis back,
With his sinuous track letting him see past the cowl. “A Waco UPF-7”, somebody says.
The old Waco’s paint is faded and stained but it’s a neat bird, it looks well maintained.
They watch as the flyer taxis around to a tiedown, pulls the mixture, shuts down.
And he climbs out, lithe, agile, with youth rediscovered, and hops to the ground.
As he sheds his leather jacket he hears his name called. “Hey, Parks, where’ve you been?
We’ve been waitin’ for you.” He grins and calls back, “You old reprobate, Lou.
The Teterboro crowd is here? The Ramapo gang, too?”
“You bet. Have some coffee. We’ll get caught up soon enough. And you can tell us,
What the hell is this GPS stuff?” Bob chocks the old Waco and says, “Sorry, Lou,
But I’ve got to find Madeleine, and my grandson, too.”
“Go ahead, Bob,” Lou says, “We’re here every day. Come by in the morning.
The tanks will be full. The oil will be topped up and she’ll start, the first pull.
Bring your grandkid around. You can teach him to fly.”
With a glance at the sky, he walks through the gate – then runs to join the one who waits.
There’ll be no more cross-countrys, no reason to roam.
The pilot’s gone West; he’s found his way home.