News: Added Links For Twin Commander and Facebook Pages

Login  |  Register

Author Topic: 680FP and IGSO 540's LOP Question  (Read 1886 times)

ghancock

  • Administrator
  • Hero Member
  • *****
  • Posts: 1123
680FP and IGSO 540's LOP Question
« on: October 07, 2015, 01:06:33 pm »
I've not been able to find any information on how to properly fly these engines as far as fuel flow goes.  Is there anything out there that might describe best practices with the Simmons fuel injection?  I fly LOP in my 310 pretty much all the time and have pretty good results with it.  Just wondering how you tweak your fuel flow with the Simmon if its constantly changing its parameters.

Thanks,

Glenn
« Last Edit: October 07, 2015, 05:25:37 pm by ghancock »
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

Willis

  • Full Member
  • ***
  • Posts: 156
  • Retired: Engineer; PE, PhD, Professor Emeritus
Re: 680FP and IGSO 540's LOP Question
« Reply #1 on: October 08, 2015, 10:21:08 pm »
To start with I always go to the Type Certificate Data Sheet for the make/model of interest.  For the 680 series its
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgMakeModel.nsf/0/A48963AE2D90905E86257D240051C9AD?OpenDocument

Now, wrt the Simmons fuel injection, (IIRC) the fuel servo portion is pressure compensated; meaning that it retards the fuel flow as the air pressure decreases.  That means for takeoff and a normal climb, then the mixture is full forward.  In this detent, it is compensating.  Once you reach your cruising altitude, then you set power (MP, RPM, mixture).  **** This is where my memory gives out.  I dont recall how one sets the mixture except by EGT/CHT like any other engine.

A good question would be: "Who overhauls Simmons equipment?"
-Bud

ghancock

  • Administrator
  • Hero Member
  • *****
  • Posts: 1123
Re: 680FP and IGSO 540's LOP Question
« Reply #2 on: October 09, 2015, 07:50:02 am »
And that is a very good question which leads to the next question.  Can these engines be converted to a normal fuel injected system or am I forever stuck on the Simmons?  You'd think the owner manual would have some mention of this but I've been pretty blown away at how almost useless the Commander Owners manual is compared to the other vendors.

Glenn
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

Willis

  • Full Member
  • ***
  • Posts: 156
  • Retired: Engineer; PE, PhD, Professor Emeritus
Re: 680FP and IGSO 540's LOP Question
« Reply #3 on: October 09, 2015, 12:19:02 pm »
I havent heard many BAD things about the Simmons system other than they fell out of fashion. 

I think they were more expensive to build and sell.  Others like Bendix had deeper pockets and could make a cheaper system so they got the lions share of the market.

The Simmons had the benefit of low Pilot workload.  No fiddling with mixuture except to tune the cruise.

Nowadays, the biggest downside is the cost of repairing/maintaining such rare swiss watches.

I agree, a system which is easier and more cost effective to maintain would be nice;  Even if it means I have to do more to manage the engine.

How to:

YIm guessing you need to (a) look for an STC on the subject.  (b) find another application with the same engine core but the injection system you want, and use that design as Engineering Data for a Field approval for a 337 mod.

-Bud