Starting procedure and "alternate air"

The world's most famous high performance general aviation aircraft
User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Starting procedure and "alternate air"

Post by guillaume78150 »

I fly the 520 verson. I'm not sure to understand what is described in the cold starting procedure. It says "full throttle" but, even with the pump running, I have to crank the engine for at least 20/30 seconds and when it starts, the engine jumps to 1500 RPM before I can reduce. Not very good on a cold engine. No priming on a fuel injected engine ?
What is the purpose of the "Alternate air" stuff on the Dashboard ? The pilot guide refers to "Alternator air" but with no further explanations (unless I missed it).

Thanks.

User avatar
AKar
A2A Master Mechanic
Posts: 5208
Joined: 26 May 2013, 05:03

Re: Starting procedure and "alternate air"

Post by AKar »

Use of full throttle is when priming. During actual starting, have it partially opened as usual.

Alternate air control provides air from the engine compartment to the engine induction, bypassing the air filter. No much use in the simulator, I recon.

-Esa

User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Re: Starting procedure and "alternate air"

Post by guillaume78150 »

Thanks Esa, how priming the Bonanza engine ? Cranking with no ignition ?

Tomas Linnet
Senior Master Sergeant
Posts: 2286
Joined: 05 Nov 2013, 10:48
Location: Oksboel, Denmark

Re: Starting procedure and "alternate air"

Post by Tomas Linnet »

just follow the checklist on page 70 in the manual:
ENGINE STARTING
1. Mixture - RICH
2. Prop - FULL
3. Throttle - FULL
4. BAT and ALT switches - ON
5. Check Gear Lights - GREEN
6. AUX Pump - ON until ff goes into the green then OFF
7. Throttle - Cracked ¼” (Clear prop!)
8. Mag/Start Switch - START
Kind Regards
Tomas

Sim: FSX SE
Accu-Sim aircraft in my hangar:
C172, C182, P51 Civ, P51 Mil, B17, Spitfire, P47, B377 COTS,
J3 Cub, T6, Connie, P-40, V35B
A2A Accu-Sim Avro Lancaster Loading:............0.000003% complete, please wait.

User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Re: Starting procedure and "alternate air"

Post by guillaume78150 »

Thanks, but what does "Cracked ¼” mean ?

User avatar
Oracle427
Chief Master Sergeant
Posts: 3916
Joined: 02 Sep 2013, 19:30
Location: 3N6
Contact:

Re: Starting procedure and "alternate air"

Post by Oracle427 »

Throttle moved forward 1/4 inch.
Flight Simmer since 1983. PP ASEL IR Tailwheel
N28021 1979 Super Viking 17-30A

User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Re: Starting procedure and "alternate air"

Post by guillaume78150 »

Clear now.
Thanks !

G.

AviationAtWar
Technical Sergeant
Posts: 899
Joined: 30 Nov 2014, 19:07
Location: US
Contact:

Re: Starting procedure and "alternate air"

Post by AviationAtWar »

I get near instant starts by opening the mixture fully, throttle to 25%, run the pump until the needle stops climbing and then cranking. I get a near instant start and 900 RPM idle.

User avatar
DHenriques_
A2A Chief Pilot
Posts: 5711
Joined: 27 Mar 2009, 08:31
Location: East Coast United States

Re: Starting procedure and "alternate air"

Post by DHenriques_ »

AviationAtWar wrote:I get near instant starts by opening the mixture fully, throttle to 25%, run the pump until the needle stops climbing and then cranking. I get a near instant start and 900 RPM idle.
There was a 520 engine in the Bo I flew years ago and as I recall the procedure for a normal start was to go to full throttle, start the pump and run it until it peaked then OFF. Then go to 1/4 throttle and start.
Sounds like this is what you might be doing.
Worked fine for us !

Dudley Henriques

User avatar
AKar
A2A Master Mechanic
Posts: 5208
Joined: 26 May 2013, 05:03

Re: Starting procedure and "alternate air"

Post by AKar »

Regarding starting method of Continentals...

IO-Continentals are fuel-injected engines that feed the fuel into the engine in proportion to the RPM (simply because the fuel pump speed varies with engine RPM), and throttle+mixture positions. Throttle position alters the fuel flow into the engine mechanically as per fuel unit's adjustment, there are no means in place to measure the actual air flow going into the engine. So, given RPM + given throttle position + given mixture position = certain fuel flow, always (not speaking of altitude compensated thingies).

When you run the boost pump, the flow provided by it is obviously unaffected by the engine RPM, so it works when the engine is shut down. What affects the fuel flow into the engine are the throttle and the mixture alone. (This is why you are instructed to go full with it when priming - not really necessary, but this provides most fuel flow. Mixture is defaulted full-rich, which is the starting position.) This is the reason for different handling of the throttle during the startup of Continentals versus IO-Lycomings, which are effectively pressure carburetted engines.

-Esa

User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Re: Starting procedure and "alternate air"

Post by guillaume78150 »

It works indeed differently from the Comanche… Thanks for the explanation.

User avatar
Piper_EEWL
Chief Master Sergeant
Posts: 4544
Joined: 26 Nov 2014, 14:14
Location: Germany

Re: Starting procedure and "alternate air"

Post by Piper_EEWL »

guillaume78150 wrote:It works indeed differently from the Comanche… Thanks for the explanation.
That’s mostly because the Comanche has a carburetor and is not fuel injected. You would have to compare. It to the Cessna 182T which has a IO-Lycoming.
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

MarcE
Senior Master Sergeant
Posts: 1652
Joined: 27 Jun 2009, 03:39
Location: Southern Germany
Contact:

Re: Starting procedure and "alternate air"

Post by MarcE »

DHenriquesA2A wrote:for a normal start was to go to full throttle, start the pump and run it until it peaked then OFF. Then go to 1/4 throttle and start.
Dudley Henriques
This constantly floods my engine.. I'm still to find out the proper way I guess :D

User avatar
cristi.neagu
Staff Sergeant
Posts: 366
Joined: 22 Apr 2017, 14:53
Location: Coventry, UK

Re: Starting procedure and "alternate air"

Post by cristi.neagu »

Best way I found was suggested on this forum. Mixture full rich, throttle 50%, aux pump on until the needle just hits the green arc (don't delay, be as quick as possible), throttle 10-20%, crank. Works really well.

User avatar
guillaume78150
Staff Sergeant
Posts: 467
Joined: 08 Oct 2015, 06:07
Location: North Burgundy
Contact:

Re: Starting procedure and "alternate air"

Post by guillaume78150 »

Another trick, Don't let the engine at idle or when taxiing without leaning. Spark plugs are quickly fouled on the Bonanza.

new reply

Return to “Bonanza "V-Tail"”

Who is online

Users browsing this forum: No registered users and 9 guests