When do engines fail on takeoff?

[Piloto]

3 hours ago, Aviationinfo said:

Here’s an interesting article, shared here just for fun and to add another perspective, on setting power for climbs.  

http://www.mooneypilots.com/mapalog/powersettings.html

Nice article. On my M20J the only time I throttle back is for descent and landing. I also noticed lower oil consumption at 2400 RPM.

José

[jaylw314]

1 hour ago, Aviationinfo said:

I bet you’re right.

I believe the enrichment facility applies only to carbureted engines.  I’m just guessing but injected engines probably have a target fuel flow at full rich at max power, that provides for cooling.

I don't really know.  I think there can be an enrichment valve in fuel injected engines (I remember seeing a picture of one in a fuel servo), but I've watched my FF while advancing the throttle in my IO-360, and there is no significant jump at full throttle.

[Hank]

4 hours ago, jlunseth said:

I read that article, and speaking from the turbo point of view it made the hair stand up on the back of my neck.  I hope no offense to Bob Kromer.  But it says, "But be careful - if CHAT or Oil Temps approach 20 degrees or so of redline be ready to back off the manifold pressure."  Any non-231 pilots happen to know what the CHT redline is for a 231? I know because I visited it once upon a time.  Its 460!!!  Yikes.  Then it says," It's unfortunate, but full rich fuel flows are sometimes set by the manufacturer to cool the engine with fuel."  Its true that full rich fuel flows for turbos are set high, but the high setting does not "cool the engine with fuel."  The high setting acts in much the same way as a LOP setting (no, don't ever climb LOP), by slowing the rate of combustion, thus stretching the ICP curve out, reducing the heat generated in the cylinder and generally being much nicer to the cylinder.  He then recommends leaning to 125 ROP for climb, but says watch the temps and if they get high pull the MP.  

No wonder so many 231's never made it past 1200.  There was this idea that it was ok to let the cylinders cook up to 440 before doing anything about it.  And that full rich in the climb was just fuel inefficient because the fuel washed the cylinder and cooled it, and we wanted to be efficient, so lean it out and let the temps climb.

Climb in the turbo is full power, full RPM, full rich, fully open cowl flaps and keep your climb rate low enough to generate sufficient cooling air flow over the cylinders.  If it happens to be a very hot day an full everything is not keeping the temps down, then lower your climb rate first.

On the supposed risk of reducing power during the climb, and worrying about whether that will upset the engine, supporting the supposition that this is the reason for engine outs during takeoff, has anyone considered that the regime of flight where we most often reduce throttle is not climb, but descent and approach. So why don't aircraft fall out of the sky with regularity when we are, say, in level low altitude flight a full cruise power, and a few miles from the airport we cut the power to get to approach speed in the pattern.  Seems to me they should be falling like proverbial flies at that point.

Bob has another article on flying the turbo Mooneys. Not having one, and seeing little chance for left seat time in one, I don't recall much if what it says, other than it's different. Should be in the same location on the MAPA site, I believe.

[Hank]

I generally make these power reductions per flight when leaving the pattern:

1. A minute or two after leveling off at cruise altitude, to my desired power setting;
2. When slowing to flap speed prior to pattern entry (go to Fine Pitch if not already there);
3. After dropping gear, to initiate descent (already Fine Pitch);
4. To Idle somewhere along short final, when I have the runway made. 

When staying in the pattern, I pull power 200-300' below TPA, so that I don't blow through it . . . . This is a combination of #1 & #2 above.

I see no reason to reduce throttle or RPM in the climb. This just makes the climb longer (because with less power the climb rate is reduced) and hotter (less excess fuel for cooling, reduced airflow). WOT / 2700 from taking the runway until leveling off and accelerating to near cruise speed, then set desired power. Leaning in the climb is fine, using Target EGT.

[ArtVandelay]

I don’t know where this “excess fuel for cooling” concept came from, another OWT?
But the amount of heat gas gives off when burning vs heat absorbed during vaporization (cooling effect of evaporation) is like 100 to 1. We know excess fuel results in less horsepower, so effectively you are just burning less fuel and creating less heat.
I think the full rich just prevents detonation.
I would say you are better off trying to lean to best power and reduce climb rate enough to keep CHTs down.
Is detonation really the boogeyman now we have engine monitors that tell us how our engine is running?

[carusoam]

I think we found a new entry to the beloved LOP vs. ROP discussion...

Any way you slice it, ROP is excess fuel being used to cool things off... EGTs and CHTs.

It does this quite effectively by evaporation...

It also does this by slowing the dynamics of the flame front...

Excess fuel gets to the engine by an extra fuel jet, in the carb.

In the injected engine it is supplied by running the electric pump in tandem with the mechanical fuel pump... with the mixture knob full in.

In the IO550, it is quite sneaky, the fuel pump comes on automatically with full throttle...  so the POH says somewhere....?

 

Now Climbing LOP... that’s a tough one... that would imply climbing out at <65% hp for engine safety sake... since the mixture continuously changes as the plane climbs... adjustments would be made every 1k’...  plenty of time available, because your climb rate is going to be artificially slow by the bhp limitation....

Climbing to cruise altitude is only 15 minutes or less... Go ROP!

Best regards,

-a-

[jaylw314]

1 hour ago, carusoam said:

In the injected engine it is supplied by running the electric pump in tandem with the mechanical fuel pump... with the mixture knob full in.

Oooh, that's interesting!  I always thought the enrichment valve was tied to only the throttle position.  I can't say I can recall a difference in FF with the fuel pump on vs off at full rich, I'll check that next time...

[jetdriven]

1 hour ago, carusoam said:

I think we found a new entry to the beloved LOP vs. ROP discussion...

Any way you slice it, ROP is excess fuel being used to cool things off... EGTs and CHTs.

It does this quite effectively by evaporation...

It also does this by slowing the dynamics of the flame front...

Excess fuel gets to the engine by an extra fuel jet, in the carb.

In the injected engine it is supplied by running the electric pump in tandem with the mechanical fuel pump... with the mixture knob full in.

In the IO550, it is quite sneaky, the fuel pump comes on automatically with full throttle...  so the POH says somewhere....?

 

Now Climbing LOP... that’s a tough one... that would imply climbing out at <65% hp for engine safety sake... since the mixture continuously changes as the plane climbs... adjustments would be made every 1k’...  plenty of time available, because your climb rate is going to be artificially slow by the bhp limitation....

Climbing to cruise altitude is only 15 minutes or less... Go ROP!

Best regards,

-a-

You can climb at 90% power LOP even from brake release.  Problem is if your climbing over 5000’ the power is similar to the old 25-25 power setting.  You give up a lot of performance. I’m not sure it saves any money. 

[PTK]

I think LOP climbs can be a significant fuel saver down low say up to 12k feet or so. Above that it becomes a stretch because climb rates become lower. Looking at it another way, climb rates < 10k or so are high so time spent in climb is less. Ff is high but for less time. It would be interesting to have some figures and compare to see any savings. I climb my NA Mooney ROP and enjoy every minute of it!