BeechTalk - BT

Username Protected · **Posted:** 03 Apr 2019, 15:27

Username Protected wrote:

Flew a trip to Cancun. Plan was SDL - KHRL - MMUN. Next day MMUN - KBRO (customs) - KSDL.

I have a retired 121 Captain that I am getting up to speed. I put him in the left seat in Cancun. We get fired up and call ground for taxi. "Sorry Senor, the radar is OTS and we are holding departures and arrivals." So we ended up with a one hour ground delay, but made it to KBRO (Brownsville, TX).

Customs went fine. The FBO quick-turned the fuel and again I put my copilot in the left seat. We attended Simcom together. He is a good pilot, just needs to get used to a complete lack of automation and safety nets in a little plane.

He fires up the right engine while I am securing the door. I am standing between the seats while he fires the left. Both he and I notice that the start light does not extinguish.

He says, "we have an abnormal, should I press the disengage?" "Yes, do it"

The starter light extinguishes as part of the final phase of the start. This is when the GCU (Generator control unit) tells the starter/generator to switch from a starter motor to a generator which provides the power for the plane. When the light stays on, this means the unit is still acting like a starter. The amp gauge was showing no current generated as confirmation.

Depressing the starter disengage button sends an electrical signal to tap the GCU on the shoulder and say - wake up, time to make the switch. If that does not work, you have a bigger problem and a rare failure.

Thankfully, Simcom did a good job of covering this scenario.

I reminded my copilot that we cannot cut fuel in this failure mode (which is the immediate reaction in all other start failures). Since the starter is still engaged, the assumption is that the start control or the start contact relay is stuck closed and will not open. If you cut fuel in this scenario, the battery will now be pumping out 800 amps into a starter that won't quit.

Eventually, the starter/generator will destroy itself while the wiring will heat up due to voltage drop and the battery may do something really ugly.

So - the proper procedure is to exit the airplane, pull the battery, then cut fuel.

Thankfully, I had ear plugs in my backpack. Since it was the left engine I got the full experience. I crawled under the motor, opened the "hell-hole" tail access panel, and contemplated my life choices.

I knew that fuel was running the motor and so there likely wasn't much current on those cables. Still, grabbing onto two giant cables that carry 800 amps and disconnecting them under a running jet engine is not what I wake up for in the morning.

It worked out.

After the shutdown, I tapped the cable to the battery and the contact was still closed - spark spark.

I then pulled the J-box cover and tapped on the two relays with my flashlight hoping it would open.

No joy.

Plane will be fixed today. We found a serviceable unit nearby. The mechanics were able to troubleshoot quickly since we knew what was wrong when they arrived.

I have now been stranded twice. Piston 1 - Jet 1. I have 15X the hours in pistons. Hmmmm.

JJ,
Nicely done, no well done!!! :clap:

Seems like there should be a little safer alternative to becoming a certified/fried A&P all at once.

Username Protected · **Posted:** 03 Apr 2019, 15:29

In the CJ and Mustang there is a battery disconnect switch in the cockpit to eliminate the need to get in the hell hole.

Next time have your SIC get out and disconnect that sucker. Oh that’s right. Retired 121. Draw him a map first. :lol:

Username Protected · **Posted:** 03 Apr 2019, 15:41

This was in the 550? The CJ2 has a battery disconnect switch on the left side so you don't have to crawl under that operating engine.

Good thing you had 2 crew. Would have been more stressful if SP needing to leave the plane empty to disconnect the battery. :eek:

Username Protected · **Posted:** 03 Apr 2019, 16:09

Username Protected wrote:

In the CJ and Mustang there is a battery disconnect switch in the cockpit to eliminate the need to get in the hell hole.

At least in the CJ3/4, it’s my understanding that you cannot use the switch for disconnecting the battery for overnight parking etc as the disconnect relay pulls a small amount of current that will drain your battery. Only used for emergency. I haven’t been to CJ school so only going by what I was told by another pilot. True?

Username Protected · **Posted:** 03 Apr 2019, 16:09

Username Protected wrote:

This was in the 550? The CJ2 has a battery disconnect switch on the left side so you don't have to crawl under that operating engine.

Good thing you had 2 crew. Would have been more stressful if SP needing to leave the plane empty to disconnect the battery. :eek:

Yeah - no bueno if SP in the 550.

I wanted to be the guy pulling the plug so it didnt get botched.

I have flown with several retired 121 guys. He did a great job in not cutting fuel and asking for help (thank goodness). He has a great attitude which is most important and seems a little hard to find unfortunately.

I think a reccurent training together really sets the stage for a team and corrects any misplaced ego without conflict.

Username Protected · **Posted:** 03 Apr 2019, 17:30

Not all aircraft have the starter disengage light (although there may an AD coming out for one I know of). Have to watch for the load generating on the amp guage.

Username Protected · **Posted:** 03 Apr 2019, 19:30

Username Protected wrote:

In the CJ and Mustang there is a battery disconnect switch in the cockpit to eliminate the need to get in the hell hole.

At least in the CJ3/4, it’s my understanding that you cannot use the switch for disconnecting the battery for overnight parking etc as the disconnect relay pulls a small amount of current that will drain your battery. Only used for emergency. I haven’t been to CJ school so only going by what I was told by another pilot. True?

Username Protected · **Posted:** 03 Apr 2019, 20:01

Jesse,

Why wouldn't shutting the master off kill the power to the starter?

Mike

Username Protected · **Posted:** 04 Apr 2019, 12:03

Not Jesse, but shutting off the master would essentially only disable the panel. It doesn’t disconnect the battery, and it’s not going to disengage the starter. That was already attempted with the starter disengage button. The starter gets its power straight from the battery. If the airplane doesn’t have a battery disconnect switch in the cockpit, the only way to cut the power at that point of a hung start is to manually disconnect the battery.

Username Protected · **Posted:** 04 Apr 2019, 12:32

Username Protected wrote:

Not Jesse, but shutting off the master would essentially only disable the panel. It doesn’t disconnect the battery, and it’s not going to disengage the starter. That was already attempted with the starter disengage button. The starter gets its power straight from the battery. If the airplane doesn’t have a battery disconnect switch in the cockpit, the only way to cut the power at that point of a hung start is to manually disconnect the battery.

Agree with all except the start spooled up normally (vs a hung start). At the end of the sequence, the start relay would not unlatch. Yesterday, after removing the relay we got it to work temporarily. Replaced with a serviceable unit and down the road we went.

Username Protected · **Posted:** 04 Apr 2019, 12:38

I understand what you’re saying. Your start was complete versus hung up by the starter. Wrong choice of words on my part.

Username Protected · **Posted:** 04 Apr 2019, 12:51

Username Protected wrote:

Jesse,

Why wouldn't shutting the master off kill the power to the starter?

Mike

Study the electrical diagram below for the 550. Note the Battery switch in the middle. It connects the battery to the battery bus.

When you press the Engine Start button it closes a relay that connects the starter/gen directly to the Hot Battery Bus. Only de-energizing the starter relay or disconnecting the battery will remove power from the starter.

This is done to bypass the 225 amp current limiters between the battery bus and the left and right main DC busses during the start.

Attachment:

C550 Electrical Start Diagram2.jpg

Username Protected · **Posted:** 04 Apr 2019, 14:47

Username Protected wrote:

Jesse,

Why wouldn't shutting the master off kill the power to the starter?

Mike

You are typed in the 500 series. You should know this MT. Massive issues if you just go to cut off and turn off master. This is something covered in school and the sim routinely. I can’t recall if you actually went to school/SIM actually. If not you should.

It such a nice upgrade to have a way to resolve this from the cockpit ala 510/525.

Username Protected · **Posted:** 04 Apr 2019, 17:10

Allen, nice job posting the electrical diagram. It's easier to see graphically that if a starter relay gets stuck closed, the starter circuit is going to remain energized until the battery is disconnected.

Username Protected · **Posted:** 05 Apr 2019, 09:53

What is the benifit to not having a relay right after the battery before any power gets distributed out?

Flying the Citation II