Skyhawk Emergency Checklist Question...

K

KennyFlys

Guest
I'm here writing a long, drawn out checklist for the 2001 172S Skyhawk. The boss wants everything that's in the POH so I'm doing that. I'd make them use the POH if it weren't so bulky. Or, they could by one produced by Cessna at some ungodly price. But, I want one in every student's hands to have and to hold and to cherish. So, I've got several hours into this task being undertaken with no remuneration expected.

Now, I'm near the end and working on the Emergency checklist area, in particular the engine fire during start. So, here's my question...

First item on the list:
1. Ignition Switch - - - - - - - - - - - Start, Continue Cranking
To get a start which would suck the flames and accumulated fuel into the engine.
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This is a fuel injected engine. From where is the fuel going to come from that you're attempting to suck back "into the engine"?

I'll buy this for a carbureted engine but it sure isn't making sense right now.
 
If you overprimed using the aux-fuel pump? Or maybe Primed while the engine was still hot, even though it wasn't needed? This could flood the engine and provide you the excess fuel situation.

Ted may be able to lend insight here.
 
Does it matter? :tongue: If the man says crank, you crank. Nobody gets in trouble, airplane is just sitting on the ramp anyway, so easy to evacuate if it doesn't work. If worse comes to worse, watch it burn from a safe distance. Just don't forget the checklist, so you can prove you were doing as instructed.

KennyFlys said:
I'm here writing a long, drawn out checklist for the 2001 172S Skyhawk. The boss wants everything that's in the POH so I'm doing that. I'd make them use the POH if it weren't so bulky. Or, they could by one produced by Cessna at some ungodly price. But, I want one in every student's hands to have and to hold and to cherish. So, I've got several hours into this task being undertaken with no remuneration expected.

Now, I'm near the end and working on the Emergency checklist area, in particular the engine fire during start. So, here's my question...

First item on the list:

This is a fuel injected engine. From where is the fuel going to come from that you're attempting to suck back "into the engine"?

I'll buy this for a carbureted engine but it sure isn't making sense right now.
Click to expand...
 
smigaldi said:
Throttle body
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Throttle body injection systems are called "pressure carburetors" on aircraft engines. A true fuel injection system as found on many TCM and Lycomings injects into the intake manifold side of each cylinder's intake valve. From there fuel will run back into the manifold.
 
lancefisher said:
Throttle body injection systems are called "pressure carburetors" on aircraft engines. A true fuel injection system as found on many TCM and Lycomings injects into the intake manifold side of each cylinder's intake valve. From there fuel will run back into the manifold.
Click to expand...

Makes sense... if there's a plenum space outside the cylinder where air and fuel mix, it can get flooded... right?

BTW, Ken: don't forget to add a warning to not use that pump for a hot or even warm start... maybe in big bold type. Seems very easy to flood those systems then kill the battery, between "primer" shots with the pump and cranking the starter. I know some idiot who did that more or once because it was not shouting out from the checklist... *cough*
 
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At the very least I suppose this cranking could reduce the amount of fuel availible by passing it out the exhaust even if the flames don't get sucked in.
 
lancefisher said:
Throttle body injection systems are called "pressure carburetors" on aircraft engines. A true fuel injection system as found on many TCM and Lycomings injects into the intake manifold side of each cylinder's intake valve. From there fuel will run back into the manifold.
Click to expand...
Did not know that. TNX!

How does the throttle work in such an engine? Is it just purely making the fuel pump push more fuel into the cylinders? :dunno:
 
rottydaddy said:
BTW, Ken: don't forget to add a warning to not use that pump for a hot or even warm start... maybe in big bold type. Seems very easy to flood those systems then kill the battery, between "primer" shots with the pump and cranking the starter. I know some idiot who did that more or once because it was not shouting out from the checklist... *cough*
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Back in Gainesville, GA, a renter was not far from the building and had hit the fuel pump. With other noise, it wasn't picked up right away but a couple of us began wondering what the buzzing was. He had the fuel pump on for more than a minute. One of the CFIs ran out there to keep th guy from starting up and make him sit for ten minutes or so while the fuel evaporated. It was dripping from under the cowling.
 
smigaldi said:
Did not know that. TNX!

How does the throttle work in such an engine? Is it just purely making the fuel pump push more fuel into the cylinders? :dunno:
Click to expand...

I'd be happy to explain how it works, in painful detail, on a car but I'm not sure if the technology is the same on a plane so I'll refrain from opining.
 
smigaldi said:
Did not know that. TNX!

How does the throttle work in such an engine? Is it just purely making the fuel pump push more fuel into the cylinders? :dunno:
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The throttle controls airflow, and a link rod from that controls a fuel flow valve. Fuel is injected under pressure into the intake port immediately ahead of the intake valve; it's flowing ALL THE TIME, not pulsed as in automobile systems. A cloud of fuel mist develops in the intake port and is sucked into the cylinder every time the intake valve opens. When you open the throttle, the airflow increases and fuel increases along with it so no accelerator pump is necessary.

The whole affair is mechanical, except for an electric boost pump. No fancy electronics or computers, not as long as those things tend to fail.
See this schematic: http://www.sacskyranch.com/rsaschematic.jpg
Note that the fuel controller labelled "Section A-A' is just another view of the fuel control which is part of the throttle body at its lower right.

Priming is achieved by opening the throttle a bit, pushing the mixture rich, and turning on the electric pump. Fuel squirts into the intake ports through the injectors. Too much of it, and it runs down the intake runners and out the throttle body into the induction tubing or maybe into the cowl, where a backfire sets it off. Keeping the engine cranking has a good chance of starting it and the cooling air might snuff it and intake air might suck it inside the engine where it belongs. Seen it done, too.

Dan
 
smigaldi said:
Did not know that. TNX!

How does the throttle work in such an engine? Is it just purely making the fuel pump push more fuel into the cylinders? :dunno:
Click to expand...

The throttle does exactly the same job on a pressure carb as it does on a port injection system, it creates a pressure drop whenever it's not fully open and the engine is turning. The further it's closed (and the higher the RPM) the greater the pressure drop and therefore the lower the manifold pressure. Lowering the MP decreases the weight (not volume) of the air passing through the engine and that's what limits engine power output.
 
KennyFlys said:
Back in Gainesville, GA, a renter was not far from the building and had hit the fuel pump. With other noise, it wasn't picked up right away but a couple of us began wondering what the buzzing was. He had the fuel pump on for more than a minute. One of the CFIs ran out there to keep th guy from starting up and make him sit for ten minutes or so while the fuel evaporated. It was dripping from under the cowling.
Click to expand...
Uh, yeah... there's that factor, as well. :D THAT I've never done, and I'm surprised the pump had enough power abvailable to last that long. :D

The key with training pilots to use these "fuelies" is to get them to think of the pump as serving the same purpose as the old hand-operated primer pump, with consideration of the fact that if you leave it on, it'll just keep pumping.
 
Ken, I have been writting my own check lists for the 172 G-1000 but have not done the Emergency yet. If you have it typed up would you be interested in swaping some files? My is in word for the start-up and before-takeoff with some modifictions for the correct steps not in the POH.
 
SLO-Mike said:
Ken, I have been writting my own check lists for the 172 G-1000 but have not done the Emergency yet. If you have it typed up would you be interested in swaping some files? My is in word for the start-up and before-takeoff with some modifictions for the correct steps not in the POH.
Click to expand...
You want me to share my hard work without compensation???? Gosh! I suppose I can do that. I teach all the time without charging the full boat. See thy PM!

Note: Chocolate fudge ice cream is acceptable remuneration. :)
 
john smith said:
When you create your checklists, do you use the "flow" method?
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While teaching the King Air sim sessions, I watched pilots struggle with the checklists, as the written numerical sequence bore no correlation to the diagrammed arrows (on a prior page) that showed a flow check. As a test, I obtained a copy of the instrument panel wall art, and sequentially numbered the gage or function to correspond with the manufacturer's list, then connected the numbers with a straight line using red ballpoint pen.

The panel picture quickly disappeared in a sea of red ink, and IIRC the pilot's eyes crossed the panel 51 times before takeoff. That seemed to be a few more than absolutely necessary, so I re-wrote my own checklist to match the flow. Although I couldn't teach it (Part 142 schools are required to adhere to mfr's materials) I was legally able to point out that the flows in the CRH didn't match the check list and as Part 91 operators they had some flexibility in that regard, and if their check list was on file at the center, they could use it for training.

Along the way I was reminded of a lesson I received once from an old timer (which by magic I have now become). He said no matter what you are flying, once you are in the seat, just put your right hand on the floor between the seats. Something will probably be there (fuel selectors, flap handle, Jepp book, pax seat belt buckle (now where's the other end?) old coffee, whatever. Then move your hand forward until it hits something, then up to the lower panel and make the CW circle until you're back at the starting point. It still works, with some obvious sub-loops for overheads, O2 behind the seats, etc. I still use the same basic flow in everything I fly, so far haven't found anything that doesn't fit. YMMV.
 
john smith said:
When you create your checklists, do you use the "flow" method?
Click to expand...
When it comes to the procedures on preflight, pre-start, start, taxi and before takeoff, use the check lists, period. The only exception is before takeoff if holding short for any duration, do a flow to re-verify, particularly with regard to the DG. For pattern work and on final, I teach use of flows but verify it with the checklist where possible. But, a checklist should be visited at least once during all phases of flight or as required for the particular aircraft flown. In cruise, it should be a periodic measure at least every thirty minutes.
 
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