cosync
Posts: 635
Joined: Sat Nov 17, 2001 7:53 pm

Start On Left Magneto

Sun Apr 07, 2002 2:29 am

i read on a site about the gruman gougar. and it said to start the engine on left magneto then switch to both.
how is this possible if the starter switch positions are left right both and start?
 
radarbeam
Posts: 998
Joined: Fri Mar 01, 2002 9:00 am

RE: Start On Left Magneto

Sun Apr 07, 2002 3:05 am

Wow, a post about the Cougar. I can't unfortunatelly answer your question but do you know it's a rare plane? There are 4 in Canada, which 2 are own by my school.


Click for large version
Click here for full size photo!

Photo © Pierre Langlois



But if you want I can ask around...
 
T prop
Posts: 910
Joined: Tue Apr 03, 2001 4:33 pm

RE: Start On Left Magneto

Sun Apr 07, 2002 3:38 am

When the mag switch is held in the start position the right mag is grounded, this leaves only the left mag hot for starting. As soon as the switch is released to both, the ground is removed from the right mag and both are hot.

T prop.
 
Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: Start On Left Magneto

Sun Apr 07, 2002 6:56 am

Most twins don't have the same type of mag switches as most singles do. Their starter switches are independent of the mag switches, so you can select the mags that you want to fire when you're starting the engines.

 Big thumbs up
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
 
cosync
Posts: 635
Joined: Sat Nov 17, 2001 7:53 pm

Sorry Guys It Was The Tiger

Sun Apr 07, 2002 5:01 pm

sorry guys i got it wrong it was the grumman tiger... Smile
derrrrrr
 
XFSUgimpLB41X
Posts: 3960
Joined: Fri Aug 25, 2000 1:18 am

RE: Start On Left Magneto

Sun Apr 07, 2002 5:07 pm

Speaking of a Cougar.. there was one here today. That is a BEAUTIFUL airplane. I love the wings on it, they are so clean- reminds me of the look of a Challenger's wing. The tail has a very handsome stance and makes it really stand out on the ramp kind of like the way a King Air 200 does (to me at least). The cockpit is pretty nice, though the one I saw did not have a slaving system nor flight directors. It did have a very nice digital engine control set-up and a good King GPS (i'll take a Garmin 530 any day over King, though).

The Cougar was here for the airplane auction we had, I'm not sure how much it sold for or if it sold. I hear there were only about 100 made.

Anybody ever flown one before? The only gripe ive heard about it is its single engine climb performance.
Chicks dig winglets.
 
T prop
Posts: 910
Joined: Tue Apr 03, 2001 4:33 pm

RE: Start On Left Magneto

Sun Apr 07, 2002 6:27 pm

Useless trivia about the Cougar: The reason that it looks clean is that it's skins are BONDED rather than riveted to the stringers and frames.

Did you hear the one about the paint shop that used paint stripper on a cougar?...

Ralgha, yes it's true that lots of GA recip twins use seperate mag and start switches, however they operate similar to the combined type. In a twin with the seperate mag switches all the start checklists I've seen so far say MAGS... both on. Reason is that when you hit that start switch you not only energize the starter but you ground the right mag. The purpose of that is to let the left magnetos impulse coupling or spark shower system fire the plugs with a hotter spark and later ignition timing. This makes engine starting easier and avoids damage from kickback. When the start switch is released, the right mag is hot again and starts firing.

The only way that an engine could start on right mag alone is if it has an impulse coupling or spark shower system on the left and right mags. Also the start switch would have to be wired so as not to ground the right mag. I suppose its possible and I believe Lycoming allows it, but I have yet to see an engine like this.

Now that I've said all this, someone's gonna come along and show me an airplane that has no impulse couplings or spark shower system... Embarrassment

T prop.

 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

Left Mag / Impulse Coupling

Sun Apr 07, 2002 9:19 pm

Hi Cosynch, and T prop: Buzz here. You got the answer to the question. A lot of flat piston engines have that impulse coupling on the Left mag - it delays the spark and spins the magneto faster for a reasonable start at slow cranking speed.

When Cosynch was talking about cat names on Grumman aircraft (cougars, tigers) i was thinking of the F9F Couger that Dad had flown in the 50's a Navy single seat carrier based fighter. Then you said Grumman Tiger, and ther was the F11F, Blue Angels were flying them when i was in diapers.

OK T-prop, i play with an Aeronca Champ, 65 thundering horsepower, hand -prop her to start, and nothing special on the mags. It can be done, but it's not for the impatient sort of aviatior.
g'day

Buzz Fueslsausage; Line Mechanic by night, DC-3 Crew CHief by choice
 
radarbeam
Posts: 998
Joined: Fri Mar 01, 2002 9:00 am

RE: Start On Left Magneto

Sun Apr 07, 2002 10:19 pm

I should fly on one in a few month for my Multi-IFR, I'll let you know how this baby handles. Everytime I pass by them my eyes are glued to it, it's a beautiful airplane!
 
erj-145mech
Posts: 305
Joined: Tue Oct 02, 2001 4:21 am

RE: Start On Left Magneto

Mon Apr 08, 2002 9:30 am

My Skymaster has dual impulse couplings, so start is on both mags, same as Piper Seneca's. Basically, aircraft with TCM IO-360 series engines are that way.
 
wilcharl
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: Start On Left Magneto

Mon Apr 08, 2002 12:47 pm

Has anyone out there flown the Couger, I havent but Ive flown the tiger, landing it with a laminar flow wing is unique and i think difficult .. a very sterdey bird... the steel cross member going through the wing/fuseualge is like a steel sewar pipe. and the laminated aluminum is beautiful and rivitless. what happend when the painter stripped the paint on the grumman? just curious
 
wilcharl
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: Start On Left Magneto

Mon Apr 08, 2002 12:53 pm

some text on it from the grumman gang webpage

On engines equipped with only one impulse coupling, you should always start with only the impulse-coupled mag enabled. Note that on many aircraft, turning the key to "start" does this automatically.

The reason is that a non-impulse-coupled mag (normally the right mag), if it fires, it will fire far too early causing the engine to try and turn backwards (the reason this isn't a problem once the engine is running is that the engine is turning fast enough to catch the combustion event just right if the mag starts it before the piston reaches top-dead-center).

Faster cranking speed will just make it more likely that the non-impulse-coupled mag will fire, which it will do too early.

So, the procedure should normally be: mags on left, mash the starter button, after you release the starter button, mags on both.

Of course, if you have impulse couplings on both mags (like my Tiger), you can start on 'both'. If you're not sure what you have, it's not hard to tell on most Lycomings. Look at the back of the engine where the mags are bolted on to the accessory case. If the mag has an impulse coupling, there'll be about a 1/2" spacer between the base of the mag and the accessory case; if it doesn't have one, the mag will be right against the accessory case.


The grumman doesnt have a start switch but a start button
 
T prop
Posts: 910
Joined: Tue Apr 03, 2001 4:33 pm

RE: Start On Left Magneto

Mon Apr 08, 2002 3:57 pm

Wilcharl,

I don't know how true this is but I heard it a few times years ago.
Story on the stripped cougar is that a shop somewhere got one of these in for a paint job. I guess they were supposed to mask off any laps or joints on the skins so as not to allow the stripper to attack the bonding adhesive, they didn't. Anyway a while after it's painted, skins start to come loose here and there and the airplane never flys again.

Buzz, yeah I figured soon as I posted some one would come up with airplanes that have no starting aids or dual impulse couplings like that tiger.

T prop.

 
wilcharl
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: Start On Left Magneto

Tue Apr 09, 2002 3:27 am

that probley explains the poor strip job they did on the Grumman that ive rented. you can clearley see the old paint strips and registration # underneeth... i guess thats why the paint shop has insurance, though I would be very upset if i took a plane in for a paint job, and the plane was totaled because of igonrance

Who is online

Users browsing this forum: timz and 18 guests