Ones and Zeros

Pulled the battery today.  Did it today instead of tomorrow as the winds are going to be pretty stiff around here tonight and tomorrow.  The terminal area forecast for Dulles (IAD) is predicting gusts up to 49 kts tomorrow morning at 8 AM (1300Z).  DCA (National) and MRB (Martinsburg) are reporting similar but slightly lower values.  You have to get to Elkins WV or Richmond VA to see significantly lower values.  Nevermind, at the predicted 49 kts (56 mph or 90 kph) that’s more than enough.

I used the opportunity to check the tiedowns on the plane as well.  Tying a plane down is important, a surprising number of planes get damaged not while flying but during storms on the ground.  Tie downs are important enough that the FAA wrote an advisory about it (AC20-35C) and good instructors make a point of teaching them.

Chains seem very secure and last a long time, but don’t have any flex.  So when the plane surges against them there’s a very strong jerk on the plane.  That can’t be good!  We use straps like these with rachet tighteners that are good for almost 3000 lbs per strap.  Ours are around a year and a half old now, so probably should be de-rated somewhat but they’re still quite good. Back when we used ropes I used to double them against big winds sometimes.  I don’t feel the need for that now.

I pull the straps snug.  I want the strap to stretch when a wind comes, not to jerk against the plane.  Stretching is good, jerking is not.  The impact force of the jerk is very high and can damage both the tie down strap and the anchor point on the plane.

This evening there are gusts up to 38 kts so far.  When I pulled the battery it was only gusting up to 25 kts.  A friend at the airport was kind enough to help with the cowling.  The battery’s in the engine compartment under the front cowling.  It’s not like a car’s hood - there’s about 25 or more screws holding it on and it’s picky about fiting correctly.  And with a wind that large piece of sheet metal can act like a nice sail.  I had a plan for doing it myself, but two people make the job easy.   So thanks “Dutchman”!

It was too cold with the wind chill to spend time looking at cables today; that’ll be for later.  And how’s the battery?  The open-circuit (no load) voltage is 11.7, that’s low, but not drastically so.  Sounds more and more like a cable and grounding problem.

Planes and cars are different.  I’m stating the obvious there.  But planes are more weight-sensitive than cars.  So plane batteries are smaller.  They’re just barely large enough to start the plane with little reserve over that.  Planes also sit outside and unused for longer periods than many cars do.  So the batteries have more time to self-discharge (aka lose charge).

Some cables used in planes were (for a time) aluminum cables.  Lighter, but not as conductive as copper.  Connections in cables and grounding get surface corrosion and don’t conduct very well.  Planes sit longer and get more chance to get this bad connections.

Cars are started with the  clutch in to separate the engine from the load.  Planes have no clutch.  If the engine turns, the prop turns and loads the engine.

So all of this makes starting more of a challenge.  And, there’s the idea that airplane engine tech is roughly 20 years behind cars.  The lower economic incentive combined with the FAA certification process (instituted for very good and valid reasons) has had the effect of limiting some technology applications in small airplane engines.

On the flip side, planes have an alternator to make current to recharge the battery and run the electronics.  But they also have a magneto to make power for the spark plugs too.  You can turn off the master switch in a plane with no problems.  Well, your radios and lights will stop working.  ATC might be concerned of course, but your engine will be fine and not notice a thing.  I had an instructor do this in flight to make that lesson clear.

What’s more useless than a plane stuck in the snow?  A plane that won’t start.  Like last winter we’re having problems again.  We (the owners) have replaced the starter, the battery, and the voltage regulator based on expert mechanic’s advice and debugging.  But it’s still having problems turning over in colder weather when left idle.

The clock draws power even when the master switch is off - but I figured that to be about a 1/2 Watt-hour per week.  Not enough to be a sole cause to this problem.  Granted it’s in the mid 30s when I tried to start it (about 2 degC).  The battery’s useable charge is about half its rated charge level at this temperature, this pushes something else marginal just too far and the engine won’t turn over.  If the engine turns over, it’ll catch reliably though.  So not an engine problem.

Ok, that leaves the charging system.  Which we’ve replaced a lot of already.  That leaves connections and cables.  The greybeards on a local pilot’s email list are recommending (from their experience) to check the grounding connections especially.  Of course current needs a full circuit path from the battery, to the starter motor, back to the battery.  If the ground connection is bad, that return path doesn’t work well.  The starter motor draws around 200 amps.  This means that any small resistance creates a large voltage drop. (Ohm’s law: V = IR)

So when I can (weather and work permitting) I’ll charge up the battery, check cables during cranking, and verify grounding connections.  I’ll also validate the components in the system too.

When I first heard of the crash this morning I paid attention.  We used to live there.  Turned out we lived about 2 miles from the crash site for a while.  After reading Joe Stack’s screed and looking at his website on the Internet Archive it’s clear he was mentally ill.  His illness is not an excuse for what he did, but it helps to understand it.

He was upset about some IRS rulings and changes in the tax code that made it harder for independent contractors and helped “body shops” or contracting houses.  He felt singled out in this and it affected him personally and financially.  Those changes affected probably well over a hundred thousand people, myself included.   Most of us just adapted our business models.  That’s life.  The world changes around us and we adapt.  That’s how it works.

Stack complained about financial problems.  He owned a house, a plane, and rented a hangar.  Many well-off pilots rent or share plane ownership.  So Stack wasn’t lacking cash at all. Yet he still felt persecuted.

He felt that politicians and big business were riding roughshod over small business people and taking advantage of taxpayers.  Basically Stack seemed to think that decisions were being made without considering their affect on most people.  True enough perhaps.  But his actions were abhorrent and vile.

He decided to burn his house, and attack an IRS office with his plane.  He didn’t consider the effect of his actions on his neighbors, his wife and daughter, nor the innocents in the IRS office, nor the other offices, nor the owners of the building, nor anyone else at all.  He’s exactly guilty of what he accused others of doing.