Jabe:

I appreciate the time you took to post that comprehensive response. I am very familiar with FADEC and have in my possession a complete installation manual which is almost 6" thick as well as an operations manual. I have studied them. First, let me say that I think that the success of getting FADEC through the certification maze is nothing short of phenomenal and Steve Smith, et. al. deserve huge applause and recognition for that effort.

Please allow me to respond in text.

On Nov 24, 2004, at 10:07 PM, Marvin Kaye wrote:

Posted for "Jabe Luttrell" <JabeLuttrell@comcast.net>:

Hello Walter,
I'd like to correct your misinformation you may have about the IOF550
tuning. The PowerLink(TM) FADEC engine is tuned to operate at the minimum
fuel flow that achieves the maximum power at all power levels above 75%
(called Best Power), including takeoff and climb.

First, FADEC does a GAMI lean test routinely to balance the F:A ratios. Sound familiar? Second, going to best power at full power is a very, very bad idea. You are correct. FADEC sets Best Power at takeoff. CHTs will climb very rapidly and continue to do so until FADEC sees CHTs in the 430-440dF range. This results in extremely high ICPs and unnecessarily high CHTs that are not experienced in non-FADEC controlled engines. This concept is ill-conceived, in my studied opinion, based on a lot of time recording this data in the most advanced engine test facility in the world.

It monitors cylinder head
temperatures and exhaust gas temperatures and enrichens the mixture if the
temperatures exceed control limits (the control limits are less than rated
limits). Its maximum enrichment is the rated full rich mixture.

The rated max mixture has been shown to be inadequate if the objective is engine longevity. If longevity is not an issue, then this will work very well... like at Reno.

With
appropriately constructed baffles you know that the limits will not be
reached in climbs and the engine will operate with considerably less fuel
flow than a manually controlled engine while at the same time operating with
higher power.

If that is the case, then why have two major manufacturers not been able to get a FADEC controlled engine off the ground before the CHT redline was reached? Both chose to halt FADEC efforts as a result. One of those companies simply responded that FADEC was not yet ready for prime time. I agree. No matter how good the baffles are, the ICPs are still exceptionally high. This narrows the detonation margin and high CHTs aggravate that. We measure these effects routinely. They are not insignificant. You can gain about 5 octane points of detonation margin by keeping CHTs 50dF cooler. FADEC gives up this margin.

The FADEC controlled engine is also tuned to operate at minimum brake
specific fuel consumption between 45% and 75% power (called Best Economy).

That is not true. It is tuned to set the mixture at 40dF LOP in those cases, but unfortunately 40dF LOP is not the Best Economy setting at all power settings. Best economy is between 10dF LOP and about 70dF LOP depending on the power setting. You cannot alter that with FADEC.

It has a cockpit switch to allow the pilot to select either the Best Economy
or Best Power operating mixtures for the range of powers between 45% and 75%
of rated power.

The switch on the panel is a minimal improvement, which was added to FADEC after I personally discussed the inadequacy of the original set-up with TCM about four years ago. It is still an inadequate set-up in my opinion, since it allows only two possible mixture settings, neither of which may be optimal for a given mission.

This allows the pilot to select whether to go fast or far
at any cruise power setting.
Futhermore in cruise (between 45% and 75% power) the FADEC engine checks its
tune every time it detects the power level has stabilized. If it needs to
make an adjustment it does. The FADEC engine checks its directly monitored
temperatures and pressures.
It calculates a variable spark advance, dwell, and injection shot for every
cylinder for every combustion event. By doing so the FADEC effectively
achieves near constant EGT (constant mixture) during climb, without any
input from the pilot.

Yes, these are good concepts on average, but may not be optimal in any given situation. FADEC does a GAMI lean test and adjusts the mixture to each cylinder. It's a copy on the success GAMI has proven optimal.

The injection method is true sequential injection--a fresh shot for each
cylinder for each intake stroke.

Possibly you were not aware that TCM had developed a sequential injection fuel system over 25 years ago (maybe 30). It worked exactly as it should. They found that at the rpms these engine operate that the it became equivalent to a constant flow system! The rewards were few and the complexities great. They nixed the effort (which was the right decision, IMO) to keep things simple. It still has the same problems but is now a great marketing tool.

No pilot can monitor an engine as closely
or control the engine on a cylinder by cylinder basis for each combustion
event, adjusting for the variations not only in operation and environment,
but also for the variations in air delivery to the cylinders.
What the FADEC does prevent the pilot from achieving is off-optimum mixture
control either for minimum fuel consumption or maximum power production. It
does allow the pilot to select any power level he/she wants and to pick the
optimal way to operate at that power level. The pilot just doesn't have to
remember X-degrees LOP or ROP and never misoperates the red knob. The pilot
has direct control of the throttle and can set any manifold pressure. The
PowerLink(TM) FADEC operates equally well with single power lever or
separate throttle and propeller controls.

If you like the choice Powerlink makes for you, then the world is wonderful. If you do not like the choice it has made for any given situation, you can do nothing about it.

There has been a thread about range on the LML. The FADEC controlled
engines in flight have demonstrated from 15% to 20% less fuel flow in side
by side (formation flight and also in a twin--manual and FADEC on the same
plane) comparison with manually controlled engines.

Interesting but not accurate. At 75+% power, FADEC will burn (according to the FADEC manual) 19.2 gph. PERIOD. That's 19.2 gph at 225 HP on a 300 HP engine. I routinely burn 15.1 gph and produce the exact same 225 HP on my IO-550. Someone needs to explain to me how that equates to a fuel savings with FADEC. I routinely operate at 85% power @ 17.2 gph. FADEC CANNOT do that. It will not allow that. I regularly operate at above that power setting with CHTs cooler than FADEC by about 40 degrees! So, if we both operate at 76% power, I will be doing so on 4 gph less than you and with CHTs 40dF cooler than you. I will have an extra hour of range and my engine will be a lot happier running a lot cooler. That is not arguable. It is measurable and we have measured it.

I am convinced by the data from engine test stands and over 404 MILLION hours of flight data that engines should be run LOP at high powers and maybe ROP at low power settings--the opposite of what FADEC does-- if durability is a concern. Having CHTS go to the hot limit on every takeoff is an ill-conceived notion in my educated opinion. Every takeoff in a FADEC controlled engine takes the HCTs to their CHT operational limit. Not a single takeoff in my airplane ever has a CHT above 350dF. That's almost 100 degrees cooler. We have repeatedly observed thermal runaway at temps above 420. FADEC risks that event on every takeoff.


That equates to bigger
fuel tanks, or more payload, or money in your pocket. What isn't immediately
obvious during engine operation is that the FADEC engine also produces a lot
less lead and carbon sludge than the manually controlled engine. This means
your oil stays cleaner longer. The spark plugs stay cleaner longer. There
is no magneto repetitive service to perform. This equates maintenance cost
savings.

The only way the oil and plugs will stay cleaner is if the engine is run LOP. That is a fact. FADEC will not accomplish that running ROP.

The PowerLink(TM) FADEC is available and has been FAA certified on the TCM
IOF550B,D,E,F,G,N cross flow and updraft engines, the TCM TSIOF550E, the TCM
IOF240B, the Lycoming-Superior-Mattituck IOF360 engines (angle and parallel
valve), 12 and 24vdc, 180HP and 200HP, the Mattituck TMX-320 engine, and
some variants for fellows who weren't satisfied with those choices. It's
the only thing you'll put on your airplane that will pay you back by
reducing your costs over any other powerplant choice.
There was a thread re: diesels for the Legacy. It was reported that at
100HP it was burning 5 to 6 gph. The FADEC IOF550,too, will burn 5 to 6 gph
at 100HP. It will also produce more than 300 HP. In summary the PowerLink
(TM)FADEC achieves excellent efficiency whether for range or speed.
I put the PowerLink(TM) FADEC in my Legacy.

Jabe, I am very pleased that you are happy. I hope your experience continues to be pleasant and the system continues to fit your mission. The lack of flexibility and the up-side down concept mixture management of FADEC does not fit my mission.

Remember, if ONE of the 26 sensors fails, it takes you FULL RICH. That might not be optimal. I stated four years ago, that as FADEC was currently designed (and continues to be designed), it is unworkable in the field. I stand by that statement. Unless you can get service in Fairhope on a regular basis, if something goes wrong with the migraine of electrical circuits and sensors, you will have great difficulty in servicing it. That has already become apparent with the very few FADEC systems in the field. I wish it weren't so.

Good luck with your system. I do hope I'm proven wrong. TCM needs the success.

Respectfully,

Walter Atkinson
Advanced PIlot Seminars