Few elemantary questions

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06-11-2007 | 08:48 PM

SongMan

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From: Cessna 150 Left seat

Few elemantary questions

-On a newer Cessnas with Fuel injection versus older with Carb, why is it that you start the engine with mixture "out" on fuel injected versus mixture"in(rich) on carb equipped Cessna? Also, why is there primer on older cessnas but not recent ones?

-I notice some airport that has both ATIS and AWOS. What is the purpose of having both?

-Aircraft with mode C transponder calls tower/ground with letter "A" after aircraft type when making initial contact. I recall there being more several more letters designating different equipment on ACFT. Where can I find this index/info?

thanks!!!

06-11-2007 | 09:39 PM

the King

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From: JS32 FO

ATIS is usually a recorded broadcast. If AWOS is also available it would give you current conditions at that airport for weather. Extra resource for pilots.

You can find a list of the equipment abbreviations in the AIM I believe.

06-12-2007 | 03:21 AM

ppilot

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From: Left seat

Quote:

Originally Posted by SongMan

-On a newer Cessnas with Fuel injection versus older with Carb, why is it that you start the engine with mixture "out" on fuel injected versus mixture"in(rich) on carb equipped Cessna?
thanks!!!

Starting with the mixture at full lean forces the circulating fuel to flow back through the return system, rather than into the manifold, which can flood the engine.

Quote:

Originally Posted by SongMan

Also, why is there primer on older cessnas but not recent ones?
thanks!!!

Newer Cessnas use the auxilliary fuel pump as a primer. A primer can pop out, which can kill the engine; plus the aux fuel pump is a useful backup in the event of an engine driven fuel pump failure. It's just a better system.

Hope this helps. Good luck!

Last edited by ppilot; 06-12-2007 at 06:03 AM.

06-12-2007 | 04:40 AM

Thedude

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Quote:

Originally Posted by SongMan

-

-I notice some airport that has both ATIS and AWOS. What is the purpose of having both?

There are quite a few towers out there that don't operate 24 hrs. AWOS for when the tower is closed

06-12-2007 | 08:52 AM

rickair7777

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From: Engines Turn or People Swim

Quote:

Originally Posted by SongMan

The current AIM should list the equipment codes. Be sure to look at the newest version, the codes were changed recently due to RVSM implementation.

06-12-2007 | 07:55 PM

SongMan

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From: Cessna 150 Left seat

Quote:

Originally Posted by Thedude

There are quite a few towers out there that don't operate 24 hrs. AWOS for when the tower is closed

Sure, but what about bigger airports where tower never closes? Why would 24hr operating tower have AWOS and ATIS at the same time?

06-12-2007 | 07:57 PM

SongMan

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From: Cessna 150 Left seat

[quote=ppilot;179119]Starting with the mixture at full lean forces the circulating fuel to flow back through the return system, rather than into the manifold, which can flood the engine.

So flooding doesn't happen to carb equipped Engine since you can start the Engine with mixture rich?

06-12-2007 | 08:44 PM

oldveedubs

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From: pǝʇɹǝʌuı

Quote:

Since they are fuel injected the mixture control directly controls the fuel going into the cylinders. By controlling fuel flow to the injectors it regulates the air/fuel ratio. Mixture out keeps the engine from being flooded during the 3-5 seconds you may be cranking.

On carb equipped airplanes the mixture controls the amount of fuel entering the carb. Usually when you start carb equipped airplanes you will see some black smoke because the mixture is initially too rich. With fuel injected you want to avoid starting with full rich because there is a tendency to vapor lock causing a longer cranking time with the possibility of at least some of the cylinders being flooded.

When you use the primer on an older cessna you are injecting raw fuel into the cylinder. When you prime fuel injected airplanes you go mixture idle cut off, fuel pump on, mixture full rich for a combination of either several seconds or a fuel flow indication, mixture idle cut off. By going full rich on the mixture you are effectively squirting raw fuel into the engine on a fuel injected airplane similar to that of a primer on an older carb equipped airplane.

Quote:

-I notice some airport that has both ATIS and AWOS. What is the purpose of having both?

Usually AWOS updates minutely while ATIS is hourly disregarding any special reports. If you want to go flying during a marginal day and the ATIS is 30 mins old...call up the AWOS and see what is current. The phone number can be found in the AF/D.

The ATIS is referenced from an ASOS/AWOS station and the only significant difference is that the winds are magnetic...the ONLY weather source that has winds magnetic.

Quote:

-Aircraft with mode C transponder calls tower/ground with letter "A" after aircraft type when making initial contact. I recall there being more several more letters designating different equipment on ACFT. Where can I find this index/info?

Flight Plan Box 3
No DME
/X No transponder
/T Transponder with no Mode C
/U Transponder with Mode C

DME
/D No transponder
/B Transponder with no Mode C
/A Transponder with Mode C

TACAN only
/M No transponder
/N Transponder with no Mode C
/P Transponder with Mode C
Area navigation (RNAV with LORAN, VOR/DME, or INS)
/Y No transponder
/C Transponder with no Mode C
/I Transponder with Mode C

Advanced RNAV with transponder and Mode C
/E Flight Management System (FMS) with DME/DME and IRU positioning update
/F FMS with DME/DME position updating
/G Global Navigation Satellite System (GNSS)
/R Required Navigational Performance (RNP)

Reduced Vertical Separation Minimum (RVSM)
/J /E with RVSM
/K /F with RVSM
/L /G with RVSM
/Q /R with RVSM
/W RVSM

06-12-2007 | 08:54 PM

ppilot

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From: Left seat

Quote:

Originally Posted by SongMan

So flooding doesn't happen to carb equipped Engine since you can start the Engine with mixture rich?

Of course flooding can happen to a carbureted engine. It just happens in a different way (over priming, over pumping the throttle (I think, I've never really pumped the throttle in an airplane), etc.).

The Lycoming engine has little tiny fuel lines running from the fuel metering unit to the engine. If you start the engine with the mixture in, you're flooding the little lines and the engine with cool liquid fuel that will not easily ignite. Starting it with the mixture lean ignites the fuel/air mixture, while excess fuel is recirculated.

Don't worry overly about this...other fuel injected engines (Continentals) are started in the full rich position. I think it's just important to know and practice the proper procedures for the airplane you're flying.

06-13-2007 | 07:46 AM

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Timmay

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From: FOD

Quote:

Originally Posted by oldveedubs

Which brings me to my next question...why does my airport, which does not have a 24/hour control tower, have an ASOS that only updates HOURLY, regardless of the time of day?

The answer I used to give is because FSS used to be based on the field so they provided a local airport advisory...but now they're off the field and they don't do any monitoring so I guess it's just up to you to figure out what the weather's like.