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Recip Fuel-injected Hot Start: Why?  
User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Posted (7 years 10 months 1 week 2 days 20 hours ago) and read 6094 times:

For all of you who have ever had the joy of trying (and failing!) to hot start a fuel-injected recip:

Why do we have do go through arcane start procedures that involve turning on fuel pumps, listening for ticking noises, etc. still? I know that the technical reason is that the fuel in the injection manifold immediately vapor locks after shutdown.

However, automotive engineers seem to have taken care of this problem eons ago, even with mechanical injection systems on gasoline engines (like the Bosch one...). So why was this problem never addressed fully over in aviation land, except for the "Hot Start" section in the POH on most complex/high performance models?

Wishing for the day when we have "idiot-proof" hot starts,

Brent


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
25 replies: All unread, showing first 25:
 
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 10 months 1 week 2 days 20 hours ago) and read 6088 times:

I'm not entirely sure, but I guess it has something to do with weight, the added gizmos that make starting a car as easy as 1-2-3 add weight, and besides, we pilots want the general public to to see us as more smart and "god-ly" going over all of those checklists  smile .

But seriously, that is why you don't see power seat controls in airplanes, like you do in cars. All of the added items add weight, and that has much larger affect in airplanes than in cars.


User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 2, posted (7 years 10 months 1 week 2 days 16 hours ago) and read 6061 times:

No power seat in airplanes?
Hardly.
Cessna offered these as an option for the pilot, as early as 1966, on the first of their cabin class twins...the 411.
Beech on the QueenAir, likewise.

As for hot starts, in depends on the engine type.
TCM continuous injection engines (IO-470, IO-520, TSIO520, GTSIO520 etc) have an engine driven fuel pump mounted on the rear of the engine, with a cooling shroud around same.
After a flight, on ground, the fuel left in this pump turns to vapor, and as the pump does not pump vapor, it must be cooled with cool fuel, before it will work.
The usual procedure is...

Throttles full open.
Mixtures idle cut off.
Operate the respective boost pump, located in the fuel tank for one-two minutes, then start as a cool engine.
Works like a charm.

The Bendix injection system on certain big-bore Lycoming engines (IGSO540 series, for example, QueenAir/Aero Commander) can be started using the same procedure, with minor variations.

Generally not a problem provided the pilot is instructed properly...many are not, of course, which is a shame, as these problems are easily handled.


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 3, posted (7 years 10 months 1 week 2 days 16 hours ago) and read 6056 times:
AIRLINERS.NET CREW
DATABASE EDITOR




Quoting 411A (Reply 2):
No power seat in airplanes?
Hardly.
Cessna offered these as an option for the pilot

Surely it wasn't a popular option.......was it? I can't imagine many people would consider the benefits worth the additional weight and complexity....

Quoting 411A (Reply 2):
Operate the respective boost pump, located in the fuel tank for one-two minutes

Interesting...that seems like a long time to run the pump(s).



2H4





Intentionally Left Blank
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 4, posted (7 years 10 months 1 week 2 days 15 hours ago) and read 6053 times:

Have your instructor show you a 172SP sitting next to an older, carburated engine. You'll see something different. The fuel distributor is sitting on top of the engine and there are small metal lines going to each cylinder. Those fuel delivery lines are sitting right on top of the engine, where all the heat is going. That heat causes the fuel to vaporize in the fuel lines, causing vapor lock. I'm not too terribly familiar with continental engines (aside from the one in the Katana) but I've heard that they're a bear to start when hot.

By turning the fuel pump on, and bringing the mixture to rich you purge the lines of fuel vapor.

Also, most FI engines run very rich at low power settings. As a result you should always make sure to lean for taxi. I had wrongfully assumed that this was only a problem in the summer until I had to clear a fouled plug today in 40 degree weather.



DMI
User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 5, posted (7 years 10 months 1 week 2 days 13 hours ago) and read 6030 times:

As for the TCM engines, the problem is NOT the 'spider' fuel distribution valve on top of the engine, nor the lines running from it to the individual fuel injectors.
'Tis the rear mounted engine driven pump, and the vapor therein.
Cool that, and the engine will start just fine.
Use the procedure I outlined previously.
As for running these tank pumps for one-two minutes, this is no problem either, as these pumps on some TCM engines (in the tank) are run continuously with many of the larger turbo engines, above 12,000 feet, for vapor suppression purposes, as per the AFM.
I've never had one fail, and I've flown these airplanes for a very long time.

Power seats.
More popular than some may think, altho they are sometimes a pain to repair.
Nice to have, though.


User currently offlineAPFPilot1985 From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 10 months 1 week 2 days 10 hours ago) and read 6007 times:

This is hopefully going to become more rare in the future with the advent of more FADEC piston engines. I got the opportunity to play around with an XL-2 the other day and it was a joy.

User currently offlineBuzz From United States of America, joined Nov 1999, 697 posts, RR: 21
Reply 7, posted (7 years 10 months 1 week 2 days 5 hours ago) and read 5975 times:

Hi KELPkid, Buzz here. APF pilot has the right idea... 1960's technology in most of the fuel injected aircraft.
The problem seems to be that to install something better, you have to get it FAA Certified which is a real chore, and is rather expensive. Lots of hoops and legalities, and engineering to jump through. The FAA wants to make sure it won't fail in flight. On the ground - if you can't start it you won't crash it (grin).
So we limp along keeping older airplanes going.
FADEC's make life easy... they do the engine management for you.
g'day


User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 10 months 1 week 2 days 4 hours ago) and read 5959 times:

Quoting Buzz (Reply 7):
Power seats.
More popular than some may think, altho they are sometimes a pain to repair.
Nice to have, though.

It seems that they are only available on higher ended aircraft; the cheap Cessna 172s don't have them.

Quoting APFPilot1985 (Reply 6):

How was the FADEC, I've never flown in an airplane with the FADEC installed.


User currently offline113312 From United States of America, joined Apr 2005, 571 posts, RR: 1
Reply 9, posted (7 years 10 months 1 week 2 days 3 hours ago) and read 5945 times:

I operated Lycomings in Piper singles and twins for thousands of hours and frequent starts and had little trouble. Most people make it harder than it really is.

Most modern autos are quite easy to start so long as you follow the instructions in the owners manual. Their electronic computers assist in making it so easy. Your older Cessnas and other popular general aviation aircraft didn't have electronic computers. Most of their fuel and induction systems are just as they were originally because that's the way the FAA certified them. Very difficult to get FAA approval for aftermarket changes in Aviation.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 10, posted (7 years 10 months 1 week 2 days 1 hour ago) and read 5922 times:

Quoting 113312 (Reply 9):
Most modern autos are quite easy to start so long as you follow the instructions in the owners manual.

Many 1970's models with Mechanical fuel injection were, too...as long as you kept the system in repair  Wink

Quoting 113312 (Reply 9):
Their electronic computers assist in making it so easy.

Bosch K-Jetronic fuel injection comes to mind as being computer free in 1970's vintage cars... scratchchin 



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 11, posted (7 years 10 months 1 week 2 days ago) and read 5911 times:

I guess the fixes are out there for this problem but all add weight and complexity. Weight and complexity are not your friends when you are trying to sell low-end airplanes. (As compared with Boeing or Airbus types.) Let's say you install a processor-controlled valve-and-plumbing system that will automatically remove or prevent vapor in the fuel delivery system. Each component, every valve, line, sensor and so on represents a potential failure and added liability. And for what? To prevent a minor annoyance caused by a relatively simple procedure.

It is a problem though. I once flew a demo flight on a light twin on behalf of a development company that was planning to buy it. The boss was in the back and the dealer's pilot was in the right seat. Hot and high conditions and probably 100°C under the pressure cowl by the time we got to takeoff position. As soon as we shoved the throttles up, both engines quit! Then they were not easy to start.

I understood what had happened including the fact that the dealer's pilot was a cool-climate, flatland pilot, but the boss was seriously not impressed. He did not buy the airplane.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineMrChips From Canada, joined Mar 2005, 927 posts, RR: 0
Reply 12, posted (7 years 10 months 1 week 1 day 17 hours ago) and read 5861 times:

Quoting KELPkid (Reply 10):
.as long as you kept the system in repair Wink

Bosch K-Jetronic fuel injection comes to mind as being computer free in 1970's vintage cars

Having now owned and maintained two cars with Bosch CIS (one pure K-Jet and one KE-Jet), I can tell you that in theory everything works great, but when it breaks, it is an unrelieved pain in the ***. And parts...holy crap...I should be a majority shareholder in Robert Bosch GmbH by now!



Time...to un-pimp...ze auto!
User currently offlineAPFPilot1985 From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 10 months 1 week 1 day 14 hours ago) and read 5840 times:

Quoting N231YE (Reply 8):
How was the FADEC, I've never flown in an airplane with the FADEC installed.

It is great, you flick a switch to start it and then set the throttles for the phase of flight that you are in and automatically get the best prop, fuel and power setting for the conditions.

Quoting SlamClick (Reply 11):
I guess the fixes are out there for this problem but all add weight and complexity. Weight and complexity are not your friends when you are trying to sell low-end airplanes

I would disagree, the liberty which is designed to be both light and simple as a trainer has fadec.


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 14, posted (7 years 10 months 1 week 1 day 12 hours ago) and read 5820 times:

Anybody heard of any company that makes FADEC units for late model C172s? I've only heard of companies that will do it for the Cirruses and Diamonds so far.

User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 15, posted (7 years 10 months 1 week 1 day 12 hours ago) and read 5817 times:

Quoting FLY2HMO (Reply 14):
Anybody heard of any company that makes FADEC units for late model C172s? I've only heard of companies that will do it for the Cirruses and Diamonds so far.

Yeah, Teledyne Contintental Motors 

Seriously, a division of Teledyne Continental is/was developing a FADEC retrofit for the Lycoming O-320 and O-360 series...I remember reading it about a year and a half ago in AOPA Pilot, and getting a serious chuckle out of that  

EDIT: as I recall, the retrofit they were developing also involves replacing one of the mags with an electronic, computer controlled ignition.

[Edited 2006-10-26 07:43:00]


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 10 months 1 week 1 day 3 hours ago) and read 5795 times:

Quoting APFPilot1985 (Reply 13):
It is great, you flick a switch to start it and then set the throttles for the phase of flight that you are in and automatically get the best prop, fuel and power setting for the conditions.

Now I'm jelous  smile 

I am going to add, which I failed to state before,

Quoting KELPkid (Thread starter):
Why do we have do go through arcane start procedures that involve turning on fuel pumps, listening for ticking noises, etc. still?

This is a form of priming the engine. As stated in the C172R manual,

Quote:
STARTING ENGINE (With Battery) 1...If the engine is warm, omit priming procedure of steps 6, 7, and 8 below.

6. Aux fuel pump --ON
7. Mixture -- SET to FULL RICH (full foward) until stable fuel flow is indicated (usually 3 to 5 seconds), then set to IDLE CUTOFF (full aft) position.
8. Aux fuel pump --OFF.
9. Mixture --ADVANCE smoothly to RICH when engine starts.


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 17, posted (7 years 10 months 1 week 1 day 2 hours ago) and read 5780 times:

Quoting APFPilot1985 (Reply 13):
I would disagree

Oh, I would disagree too, but it is the manufacturer's legal department whose opinion is heard, not ours.

I was told by an executive at McDonnell Douglas who shall remain nameless, that their legal department argued vehemently against the development of the MD-80 as they felt it was a de facto admission that there was "something wrong with" the DC-9 dash ten-through fifty airplanes.

Remember also, that Cessna went nearly a decade building no single engine airplanes at all - because of liability issues.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineAPFPilot1985 From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 10 months 1 week 1 day ago) and read 5763 times:

Quoting SlamClick (Reply 17):
Oh, I would disagree too,

What I was disagreeing about was the weight and complexity issue. However about the reluctance of change in GA I agree 100%. That reluctance is why we are still seeing engines that would be more at home in the market 40 years ago still flying on a fuel that is dependent on a single factory.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 19, posted (7 years 10 months 1 week 22 hours ago) and read 5746 times:

I've flown a 172 R model exactly ONCE:

Quoting N231YE (Reply 16):
6. Aux fuel pump --ON
7. Mixture -- SET to FULL RICH (full foward) until stable fuel flow is indicated (usually 3 to 5 seconds), then set to IDLE CUTOFF (full aft) position.
8. Aux fuel pump --OFF.
9. Mixture --ADVANCE smoothly to RICH when engine starts.

I did a cold start-nothing to it. Very much like a standard 172

Turning fuel pumps off and on in a 172 just seems WRONG to me  irked  I can understand doing it in more complex models...like the 210 (which I have 30 hours in), or even complex trainers like the Arrow.

Also, I had to learn to deal with the autopilot in the R-model (at least the particular one at the FBO that I took the R-model demo ride in, with an instructor), and all the funky chimes and bells and whistles that go along with that...I suppose one day if I'm ever rich enough to fly for fun, it would be nice to be able to shoot a coupled approach  Smile Unfortunately, I didn't have enough quarters to pay the FBO $119 an hour (plus the instructor's rate) to learn  Wink

The extra $25/hr. premium over using a P-model wasn't really worth it for me. The P-models in the area all have really nice GPSes installed, anyways.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 20, posted (7 years 10 months 1 week 20 hours ago) and read 5731 times:

Quoting SlamClick (Reply 17):
Remember also, that Cessna went nearly a decade building no single engine airplanes at all - because of liability issues.

And when they came back, they were equipped with 13 fuel sumps and fuel injected engines (no carb, no carb ice). One thing the attorneys did right, beefier seat tracks. All these "improvements", and they still have plastic farings that crack after about 200 hours on the line and have pathetic quality control. I really enjoyed having that air vent fall out of the 2006 172 on our line and into my lap when it was 40 degrees...

Assuming it's a KAP140, that's the easiest autopilot to learn because it doesn't do much. And there are really only four audibles. The altitude alert, the disconnect, and the two the guy says, "Trim in motion" and "Check pitch trim".

I don't mind having an aux pump in the 172S I fly alot. In fact, coming from low wing aircraft it's kind of nice to have it there. What happens if the engine driven one fails? I hope gravity gives you enough to keep that fan turning so it doesn't get hot inside.



DMI
User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 21, posted (7 years 10 months 1 week 20 hours ago) and read 5727 times:

Quoting Pilotpip (Reply 20):
What happens if the engine driven one fails? I hope gravity gives you enough to keep that fan turning so it doesn't get hot inside.

I think you just contradicted yourself there...a non-R or SP 172 (Skyhawk XP excluded) uses gravity alone for fuel feed-no fuel pump at all. Very simple, it works very well as long as you keep >0.1 G maintained... (zero G pushovers will make the engine sputter a little in many 172s  Wink ).



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 22, posted (7 years 10 months 1 week 18 hours ago) and read 5710 times:

Oddly, the 172RG that I fly has both, yet the 172Ns I fly do not.

The gascolator and Resevoir in the carburator help assure that the engine sputtering issue you just mentioned does not happen.

[Edited 2006-10-27 01:13:25]


DMI
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 10 months 1 week 18 hours ago) and read 5702 times:

Quoting Pilotpip (Reply 20):
I hope gravity gives you enough to keep that fan turning so it doesn't get hot inside.

Hehe...why do pilots sweat when their fan doesn't work?   smile 

[Edited 2006-10-27 01:22:59]

User currently offlineErj-145mech From United States of America, joined Oct 2001, 306 posts, RR: 1
Reply 24, posted (7 years 10 months 6 days 5 hours ago) and read 5617 times:

Quoting 411A (Reply 5):
'Tis the rear mounted engine driven pump, and the vapor therein.
Cool that, and the engine will start just fine.

Not so fast there. I have a C-337 and the engine driven fuel pump is mounted on the front of the engine(TCM IO-360), and still have the hot starting/vapor pressure issues on a short ground stop. I've experimented with leaving the oil service door on the cowlings open while on the ground and that seems to help by letting the heat out of the engine compartment. The problem is that the fuel in the lines over the cylinders "percolates" and the gasoline will convert to vapor instead of liquid. The pumps only pump liquid, not vapor, and you need to purge the vapor and cool the lines with the electric fuel pump.


User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 25, posted (7 years 10 months 5 days 16 hours ago) and read 5576 times:

Regardless of the location of the EDP, it still is mounted...well, on the engine, and as such absorbes heat therefrom, when the engine is shutdown.
The spider and individual fuel lines running to injectors have nothing to do with the fuel vapor issue, only the EDP.

See www.tcmlink.com for details.
You have to register to get the information.


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