Crashes owing to low air pressure, over rich mixture

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Re: Crashes owing to low air pressure, over rich mixture

Unread post by boneman » Sun Oct 18, 2020 1:22 pm

Chalkie wrote:
Sun Oct 18, 2020 12:51 pm
southside wrote:
Fri Oct 16, 2020 10:24 pm
Chalkie, first of all, I would like to point out that I am aware you are a highly experienced pilot and always read and take in what you post.

That said...I have to disagree with you on the IO520 or even the IO550 hot start...
SS, thanks. You are allowed to disagree as this is a learning academy.

Flooding an engine should always be used when you run out of ideas. Reason: you KNOW it is flooded.

The method I described works. Try it. It just might make hot starts easier for you. Irrespective of what the POH says.
Chalkie and SS
The POH method has never worked for me, always a pain in the backside.
What I now do Is
Mixtue and throttle full forward
Fuel pump on high for 2 seconds
Throttle then open to where it was at idle shutdown. Mixure full forward
Hand on the fuel pump switch
Start and the moment the engine fires, fuel pump on high and as it start to rev up, fuel pump off.
If the engine wants to die, just a blip with the fuel pump.
Works everytime :D
Last edited by boneman on Sun Oct 18, 2020 6:59 pm, edited 1 time in total.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by Chalkie » Sun Oct 18, 2020 1:29 pm

boneman wrote:
Sun Oct 18, 2020 1:22 pm
Chalkie and SS
The POH method has never worked for me, always a pain in the backside.
What I now do Is
Mixtue and throttle full forward
Fuel pump on high for 2 seconds
Throttle then open to where it was at idle shutdown
Start and the moment the engine fires, fuel pump on high and as it start to rev up, fuel pump off.
If the engine wants to die, just a blip with the fuel pump.
Works ever time :D
Gert, whatever works for you is great. An ex-student taught me the method I described and it works.

The benefit is you do not have to crank a flooded engine till the fuel/air ratio is finally combustible.

Do me a favour and try the method I described, then give us feedback.

I too, am willing to learn.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by boneman » Sun Oct 18, 2020 1:39 pm

Chalkie wrote:
Sun Oct 18, 2020 1:29 pm
boneman wrote:
Sun Oct 18, 2020 1:22 pm
Chalkie and SS
The POH method has never worked for me, always a pain in the backside.
What I now do Is
Mixtue and throttle full forward
Fuel pump on high for 2 seconds
Throttle then open to where it was at idle shutdown
Start and the moment the engine fires, fuel pump on high and as it start to rev up, fuel pump off.
If the engine wants to die, just a blip with the fuel pump.
Works ever time :D
Gert, whatever works for you is great. An ex-student taught me the method I described and it works.

The benefit is you do not have to crank a flooded engine till the fuel/air ratio is finally combustible.

Do me a favour and try the method I described, then give us feedback.

I too, am willing to learn.
Chalkie, thanks I will give it a try next time.
As I understand it is the heat soaked fuel pump is responsible for the cavitation.
The fuel pump on low for longer time is likely your method success.
I just hate a flooded engine.
Last edited by boneman on Sun Oct 18, 2020 7:01 pm, edited 1 time in total.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by southside » Sun Oct 18, 2020 5:54 pm

Just to be clear, I was not advocating flooding the engine, I was advocating purging the fuel lines with the mixture in the idle cutoff position.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by SandPiper » Mon Oct 19, 2020 9:12 am

southside wrote:
Sun Oct 18, 2020 5:54 pm
Just to be clear, I was not advocating flooding the engine, I was advocating purging the fuel lines with the mixture in the idle cutoff position.
We used this method in our C210 charter operation with 100% success rate.
I am assuming everyone is referring to Cessna 200 series aircraft fitted with the IO-520, the C310 fuel pumps work differently also with the IO-520.
Depends from aircraft to aircraft, I suppose.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by Chalkie » Mon Oct 19, 2020 9:27 am

southside wrote:
Sun Oct 18, 2020 5:54 pm
Just to be clear, I was not advocating flooding the engine, I was advocating purging the fuel lines with the mixture in the idle cutoff position.
Then we agree. Your way might be a bit quicker, but the idea is the same: Fill the fuel system with fresh cool fuel (EDP and throttle body) then do a normal 'cold' start.

BTW, the throttle FWO makes little sense when the mixture is in ICO as the throttle barrel valve is downstream of the mixture and FF sensor is not downstream of flow divider (if used). If the FF is a pressure instrument calibrated to read FF, then yes, that pressure is taken from the metered fuel divider (spider).
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by markus_m2 » Mon Oct 19, 2020 9:40 am

Hehe, seems hot starting is as much up for debate as mixture settings ... both fit in the realm of black magic :lol:
But seriously, many advocate "religiously read the POH", and I would like to point out above two examples where the POH is NOT the bible many seem to think it is...

My hot start on the N/A 206 is similar to Boneman - throttle and mixture forward, fuel pump on for 2 sec, throttle back to idle, engage starter and slowly advance throttle till it takes (usually within 2 or 3secs, sweet spot seems to be throttle around half way in). Immediately back to idle.
There's the very odd circumstance where it will take and then a few secs later die again, at which point I just flick the fuel pump HI till it takes again, then fuel pump off...

Which brings me to Southside's post:
southside wrote:
Fri Oct 16, 2020 10:24 pm

NEVER, I say again, NEVER put the pump on HI with the engines running. It will end in tears. HI is only for start and engine driven pump failure.
I presume you're talking in-flight - engine failure due to rich mixture?
Or is there something else you're pointing out (example engine fire due to "spilt" fuel as in my case using it on the ground)?
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by boneman » Mon Oct 19, 2020 10:00 am

Chalkie wrote:
Mon Oct 19, 2020 9:27 am
southside wrote:
Sun Oct 18, 2020 5:54 pm
Just to be clear, I was not advocating flooding the engine, I was advocating purging the fuel lines with the mixture in the idle cutoff position.
Then we agree. Your way might be a bit quicker, but the idea is the same: Fill the fuel system with fresh cool fuel (EDP and throttle body) then do a normal 'cold' start.

BTW, the throttle FWO makes little sense when the mixture is in ICO as the throttle barrel valve is downstream of the mixture and FF sensor is not downstream of flow divider (if used). If the FF is a pressure instrument calibrated to read FF, then yes, that pressure is taken from the metered fuel divider (spider).
SS we agree you not advocating to flood the engine.
It just so happened that I most of the time ended with a flooded engine and a hot stater motor.
This even after the FCU and spider was reconditioned.
I just found an alternate method that works for me.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by dollar » Mon Oct 19, 2020 11:23 am

Interesting post.

I am not a pilot but know my way around an internal combustion engine.

My last truck without EFI was a 94 Isuzu. Although I have owned a multitude of motorcycles with carbs my last bigger one (2006 4 cylinder Honda) had EFI.

Interestingly the first aero fuel injection system was used in 1902. Antoinette 8v. Not sure how that worked out.

DB and BMW both used Bosch direct injection in aero engines with considerable success during WWII.

During the 1950’s fuel injection caught on for use in cars, first racing cars and then production models. This using technology developed in aviation.

Lycoming, Continental and others offered models from the early 70’s.

So - finally- my question. Why are carburetors still so heavily represented? Age of the aircraft? Cost?
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by jimdavis » Mon Oct 19, 2020 1:00 pm

dollar wrote:
Mon Oct 19, 2020 11:23 am
Interesting post.

I am not a pilot but know my way around an internal combustion engine.

My last truck without EFI was a 94 Isuzu. Although I have owned a multitude of motorcycles with carbs my last bigger one (2006 4 cylinder Honda) had EFI.

Interestingly the first aero fuel injection system was used in 1902. Antoinette 8v. Not sure how that worked out.

DB and BMW both used Bosch direct injection in aero engines with considerable success during WWII.

During the 1950’s fuel injection caught on for use in cars, first racing cars and then production models. This using technology developed in aviation.

Lycoming, Continental and others offered models from the early 70’s.

So - finally- my question. Why are carburetors still so heavily represented? Age of the aircraft? Cost?
A very interesting question Dollar. I suspect both age and cost are part of the answer. Also, the advantages of fuel injection on aircraft engines may not be that marked. Possibly because of the low revs and possibly because they run for 90% of their lives at pretty constant power settings.

I am going to do a bit of research because I understand that Lycoming and Continental use different systems. I think Lycomings use a lower pressure system that injects before the valve, while Continental's use a higher pressure into the cylinders. I will come back to you on this.

Otherwise our resident engine fundi - Chalkie - might be able to enlighten us.

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Re: Crashes owing to low air pressure, over rich mixture

Unread post by Chalkie » Mon Oct 19, 2020 1:12 pm

dollar wrote:
Mon Oct 19, 2020 11:23 am
So - finally- my question. Why are carburetors still so heavily represented? Age of the aircraft? Cost?
If it ain't broke, don't fix it. In aviation any change requires recertification and that could easily spiral out of control, expense wise so cost is a major handbrake to slow down development. The (aviation) mechanical fuel injection system is a constant flow system. EFI would increase efficiency but again, would require recertification and backup systems.

For example: about 3% of Lycoming engines develop a cracked crankcase in the area below #2 cylinder. To change the mould to prevent this from happening, would require recertification of the engine. As a result, Lycoming says, just live with it. Buy a new crankcase.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by Chalkie » Mon Oct 19, 2020 1:22 pm

jimdavis wrote:
Mon Oct 19, 2020 1:00 pm
I am going to do a bit of research because I understand that Lycoming and Continental use different systems. I think Lycomings use a lower pressure system that injects before the valve, while Continental's use a higher pressure into the cylinders. I will come back to you on this.

Otherwise our resident engine fundi - Chalkie - might be able to enlighten us.

jim
The two systems differ in the design of the fuel pump (diaphragm vs gears) low pressure vs higher pressure. Both systems use constant fuel flow through the injector nozzle which are installed in the intake, aimed at the inlet valve.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by Sunbird » Tue Oct 20, 2020 10:38 am

dollar wrote:
Mon Oct 19, 2020 11:23 am
Interestingly the first aero fuel injection system was used in 1902. Antoinette 8v. Not sure how that worked out.
Got the date wrong? Sounds French. Perhaps everyone then thought first flight was imminent at the time. Or this technology was developed then, and got used eventually.
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by ddevos » Tue Oct 20, 2020 12:19 pm

Sunbird wrote:
Tue Oct 20, 2020 10:38 am
dollar wrote:
Mon Oct 19, 2020 11:23 am
Interestingly the first aero fuel injection system was used in 1902. Antoinette 8v. Not sure how that worked out.
Got the date wrong? Sounds French. Perhaps everyone then thought first flight was imminent at the time. Or this technology was developed then, and got used eventually.

Info on this engine from 1906... https://en.wikipedia.org/wiki/Antoinette_8V
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Re: Crashes owing to low air pressure, over rich mixture

Unread post by dollar » Tue Oct 20, 2020 12:46 pm

ddevos wrote:
Tue Oct 20, 2020 12:19 pm
Sunbird wrote:
Tue Oct 20, 2020 10:38 am
dollar wrote:
Mon Oct 19, 2020 11:23 am
Interestingly the first aero fuel injection system was used in 1902. Antoinette 8v. Not sure how that worked out.
Got the date wrong? Sounds French. Perhaps everyone then thought first flight was imminent at the time. Or this technology was developed then, and got used eventually.
nfo on this engine from 1906... https://en.wikipedia.org/wiki/Antoinette_8V

Says circa 1906 so yes 1902 is not particularly accurate 😂

Point is that they had the idea in the very early 1900’s - albeit only “ manifold injection”.

Further research has revealed than many aero injection systems are purely mechanical- no electronics, perhaps a continuation of not wanting to rely on electronic wizardry 😂


You can’t easily compare aero injection systems to automotive systems - for reasons already explained to me and two other important factors- economies of scale and emission regulations. This drove automotive design from the 80’s onwards. Aircraft design did not experience this.

If you can overcome the real or perceived issues with EFI used in aircraft it sure solves a lot of problems? 😜

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