mooney mishap at Granby, Co

[EricJ]

This may also make a point about careful selection of CFIs.

 

[N201MKTurbo]

I’m not a Contintal expert by any stretch. So take what I say with a grain of salt.

The Rocket I’ve been flying lately, well I made the first three flights after an engine tear down, all cross countries.

The engine would cough and sputter at any power setting below 15 inches unless you leaned it a lot. And you had to adjust the mixture on every power change. 

I told the mechanic who was working on it that it was too rich on the low power end. He said it was right by the book. The owner had him increase the max fuel flow so it would maintain 1500 TIT in a full power climb. This was about 38 GPH if I recall. We asked him to just lean the idle side and he took 1/2 turn off the screw. It made a big improvement but it was still too rich. He took another 1/2 turn off and it ran great. He said it was way out of spec, but it ran great so we left it there. 

So it seems that raising the max fuel flow also raises the idle fuel flow and makes the factory procedure invalid. 

I’m sure the factory settings would work fine, but it does run very hot in climb. It probably also makes more than 100% power.

[N231BN]

I’m not a Contintal expert by any stretch. So take what I say with a grain of salt.
The Rocket I’ve been flying lately, well I made the first three flights after an engine tear down, all cross countries.
The engine would cough and sputter at any power setting below 15 inches unless you leaned it a lot. And you had to adjust the mixture on every power change. 
I told the mechanic who was working on it that it was too rich on the low power end. He said it was right by the book. The owner had him increase the max fuel flow so it would maintain 1500 TIT in a full power climb. This was about 38 GPH if I recall. We asked him to just lean the idle side and he took 1/2 turn off the screw. It made a big improvement but it was still too rich. He took another 1/2 turn off and it ran great. He said it was way out of spec, but it ran great so we left it there. 
So it seems that raising the max fuel flow also raises the idle fuel flow and makes the factory procedure invalid. 
I’m sure the factory settings would work fine, but it does run very hot in climb. It probably also makes more than 100% power.

Something sounds a little strange. I have a lot of time with those engines in twin Cessnas but never in a Mooney. A Ram VI making 335 Hp is only flowing 34-35 gph on takeoff and well below 1500 TIT. The Mooney rocket is only making 305 hp right?

The idle mixture setting can affect part throttle fuel flow but once WOT they should have no effect on each other. I don't know what all they changed in making that engine fit in a Mooney but that doesn't make sense.

[kortopates]

2 hours ago, N201MKTurbo said:

I’m not a Contintal expert by any stretch. So take what I say with a grain of salt.

The Rocket I’ve been flying lately, well I made the first three flights after an engine tear down, all cross countries.

The engine would cough and sputter at any power setting below 15 inches unless you leaned it a lot. And you had to adjust the mixture on every power change. 

I told the mechanic who was working on it that it was too rich on the low power end. He said it was right by the book. The owner had him increase the max fuel flow so it would maintain 1500 TIT in a full power climb. This was about 38 GPH if I recall. We asked him to just lean the idle side and he took 1/2 turn off the screw. It made a big improvement but it was still too rich. He took another 1/2 turn off and it ran great. He said it was way out of spec, but it ran great so we left it there. 

So it seems that raising the max fuel flow also raises the idle fuel flow and makes the factory procedure invalid. 

I’m sure the factory settings would work fine, but it does run very hot in climb. It probably also makes more than 100% power.

there is no way, that what is described above as being within spec. Its an emergency if TIT at full power climb exceeds 1450F! A max TIT of 1450F at full power rich is a limitation on the Rocket and all the Continental Turbo. A TIT of 1500F is way to lean. The procedures (emergency or normal) call for turning on the high boost pump should TIT exceed 1450F on takeoff (different POH's place this in different places and a lot of pilots miss it).   If its at 38 GPH already when the Rocket TSIO-520-NB should need 33-35 GPH but 38 GPH is resulting in 1500F  TIT I would suspect the FF transducer K factor must be off and perhaps the mechanic should be adjusting the upper end by the max metered fuel pressure instead of FF GPH.

Since I am overly anal about my planes setting, I am done till I see the settings I want in a trip around the pattern since I find just doing on ground only gets you close compared to what you'll see after you leave the runway in climb. 

WRT "So it seems that raising the max fuel flow also raises the idle fuel flow and makes the factory procedure invalid." absolutely right, but I wouldn't say invalid, just that one of the settings is adjusted its imperative to check the others and re-tweak till both ends are in spec. If one can't get both fuel pressures to spec, it typically means the fuel pumps needs to be sent out for repair.

WRT to the idle mixture, I am not sure what he adjusted 1/2 turn, but he can't adjust idle mixture merely by turning a screw and giving it back.  There are two Idle adjustments, the fuel pumps unmetered fuel pressure idle setting on the fuel pump done at 700 rpm - which I hope is not what he adjusted. And a separate Idle mixture adjustment screw on the servo. But the overly rich IDLE mixture, which is independent of unmetered fuel  should be tested the the same way you do it on your Lyc, by idling at 1000 rpm full rich for a minute and and then reduce to min idle of 700-725 RPM and then slowly lean till the engine dies observing the rpm rise. But rather than the 10-40 rpm rise you look for for on your Lyc RSA5 we want to see a tad higher of about 20-50 rpm rise. A very overly rich one could be 100+ rpm rise but very easy to check.  

Edited August 27, 2018 by kortopates

[kortopates]

16 minutes ago, N231BN said:

Something sounds a little strange. I have a lot of time with those engines in twin Cessnas but never in a Mooney. A Ram VI making 335 Hp is only flowing 34-35 gph on takeoff and well below 1500 TIT. The Mooney rocket is only making 305 hp right?

The idle mixture setting can affect part throttle fuel flow but once WOT they should have no effect on each other. I don't know what all they changed in making that engine fit in a Mooney but that doesn't make sense.

Agreed, RAM's current spec is 36 GPH

[kortopates]

3 hours ago, EricJ said:

This may also make a point about careful selection of CFIs.

 

Very few CFI's know how to manage high performance engines let alone turbo's - but that's not necessarily the issue with this accident. But if a CFI follows an older POH on how to run the engine as gospel that is a problem given how much more we know today about engine operation.  (I find the modern POH's are much improved with their guidance)

Edited August 27, 2018 by kortopates

[N201MKTurbo]

5 minutes ago, kortopates said:

there is no way, that what is described above as being within spec. Its an emergency if TIT at full power climb exceeds 1450F! A max TIT of 1450F at full power rich is a limitation on the Rocket and all the Continental Turbo. A TIT of 1500F is way to lean. The procedures (emergency or normal) call for turning on the high boost pump should TIT exceed 1450F on takeoff (different POH's place this in different places and a lot of pilots miss it).   If its at 38 GPH already when the Rocket TSIO-520-NB should need 33-35 GPH but 38 GPH is resulting in 1500F  TIT I would suspect the FF transducer K factor must be off and perhaps the mechanic should be adjusting the upper end by the max metered fuel pressure instead of FF GPH.

Since I am overly anal about my planes setting, I am done till I see the settings I want in a trip around the pattern since I find just doing on ground only gets you close compared to what you'll see after you leave the runway in climb. 

WRT "So it seems that raising the max fuel flow also raises the idle fuel flow and makes the factory procedure invalid." absolutely right, but I wouldn't say invalid, just that one of the settings is adjusted its imperative to check the others and re-tweak till both ends are in spec. If one can't get both fuel pressures to spec, it typically means the fuel pumps needs to be sent out for repair.

WRT to the idle mixture, I am not sure what he adjusted 1/2 turn, but he can't adjust idle mixture merely by turning a screw and giving it back.  There are two Idle adjustments, the fuel pumps unmetered fuel pressure idle setting on the fuel pump done at 700 rpm - which I hope is not what he adjusted. And a separate Idle mixture adjustment screw on the servo. But the overly rich IDLE mixture, which is independent of unmetered fuel  should be tested the the same way you do it on your Lyc, by idling at 1000 rpm full rich for a minute and and then reduce to min idle of 700-725 RPM and then slowly lean till the engine dies observing the rpm rise. But rather than the 10-40 rpm rise you look for for on your Lyc RSA5 we want to see a tad higher of about 20-50 rpm rise. A very overly rich one could be 100+ rpm rise but very easy to check.  

As I said, I’m no expert and I didn’t adjust anything. I don’t remember the exact fuel flows, but it was quite a bit higher than normal. I do remember the TIT was higher than 1500. 

I thought the TIT limit was 1650.

[kortopates]

13 minutes ago, N201MKTurbo said:

As I said, I’m no expert and I didn’t adjust anything. I don’t remember the exact fuel flows, but it was quite a bit higher than normal. I do remember the TIT was higher than 1500. 

I thought the TIT limit was 1650.

Yes, the engines have a maximum continuous TIT of 1650F and 1700F for one minute. But they also have a max HP TIT limit of 1450F (i.e. takeoff) to ensure not taking off with an overly lean mixture. This isn't always spelled out in the Limitation section - it is on the Rocket, but its typically always referenced in the procedure either in the normal takeoff or emergency procedures. 

Taking off with a TIT of 1550F is what leads to a power loss in climb shortly thereafter. I tend to see at least one every month. The ones I do see though are the ones to get back down safely. Turbo Transition training needs to include monitoring TIT (or FF). Some prefer to monitor FF,  but vapor lock can result in an erratic FF and not clearly show its  inadequate  but TIT will show right away if the engine isn't getting adequate fuel. 

And frankly I consider you more of an expert than most; understandably more of Lyc guy than continental guy. 

Edited August 27, 2018 by kortopates

[Shadrach]

Sorry for the cynicism but my sense is that the engine sputter is part of a memory audit that makes for a better story than I pooched the landing on a 5000' runway because I was way too fast due to my inexperience.  A quick search of the NTSB tells us that Mooney pilots, especially new ones are adept at driving their planes right off the ends of runways they should have been able to land on three times. An F model at my home airport suffered the same fate many years ago back when our long runway was only 5000'.  Apparently it's not that hard to do, all you need is a bit of panic, determination and a threshold speed in excess of 90kts.   

Paul, you guys have a lot of data on the mixture set up subject.  Has anyone on your end considered that these "overly rich" mixtures might be due to the APS guys suggesting that most Continentals are set up too lean at take off (I've had no reason to doubt them)?  You say too lean but both Deakin and Atkinson have both said too rich on a number of occasions. It's hard to sort out what's correct with respected opinions running contradictory to one another.

Edited August 27, 2018 by Shadrach

[carusoam]

36 minutes ago, Shadrach said:

Sorry for the cynicism but my sense is that the engine sputter is part of a memory audit that makes for a better story than I pooched the landing on a 5000' runway because I was way too fast due to my inexperience.  A quick search of the NTSB tells us that Mooney pilots, especially new ones are adept at driving there planes right off the ends of runways they should have been able to land on three times. An F model at my home airport suffered the same fate many years ago back when our long runway was only 5000'.  Apparently it's not that hard to do, all you need is a bit of panic, determination and a threshold speed in excess of 90kts.   

Paul, you guys have a lot of data on the mixture set up subject.  Has anyone on your end considered that these "overly rich" mixtures might be due to the APS guys suggesting that most Continentals are set up too lean at take off (I've had no reason to doubt them)?  You say too lean but both Deakin and Atkinson have both said too rich on a number of occasions. It's hard to sort out what's correct with respected opinions running contradictory to one another.

Great point, Ross...

What is the effect of asking a mechanic to raise the max FF rate from 27.2 gph at SL to a number like 29 or 30...?

Adding an extra gallon or two for controlling CHTs during full powered climb would be nice...

But, what would I need to expect as a result?  Being slightly overly rich? While taxiing at 700rpm...

Trying to understand the effect of setting the max FF on the min FF...

This is starting to make the set-up of carburetors look more simple. 

Best regards,

-a-

[Shadrach]

3 minutes ago, carusoam said:

Great point, Ross...

What is the effect of asking a mechanic to raise the max FF rate from 27.2 gph at SL to a number like 29 or 30...?

Adding an extra gallon or two for controlling CHTs during full powered climb would be nice...

But, what would I need to expect as a result?  Being slightly overly rich? While taxiing at 700rpm...

Trying to understand the effect of setting the max FF on the min FF...

This is starting to make the set-up of carburetors look more simple. 

Best regards,

-a-

Idle and take off mixture settings are not really connected.  That is to say that idle mixture at 700 rpm is independent of full power take off mixture.  It would take a grossly mis-adjusted fuel system to produce a mixture so rich that an engine would not deliver power...something more than 400ROP in my estimation.  The power curve is pretty flat through a large  range of mixture settings, but the CHT curve is not quite as flat.  Given the choice, I would want extra fuel available.  You can always twist the knob out, but you can't make it richer than full rich..

[kortopates]

11 hours ago, Shadrach said:

Paul, you guys have a lot of data on the mixture set up subject.  Has anyone on your end considered that these "overly rich" mixtures might be due to the APS guys suggesting that most Continentals are set up too lean at take off (I've had no reason to doubt them)?  You say too lean but both Deakin and Atkinson have both said too rich on a number of occasions. It's hard to sort out what's correct with respected opinions running contradictory to one another.

Ross, virtually the whole industry agrees Continentals are set up too lean at takeoff because of Continentals spec is on the lean side. Its a very accepted practice of adding a 0.5 to 1.0 GPH above Continentals high number when doing the set up. I can't say why Continental is a bit lean, but I've always assumed it was because they wanted to certify their engines with a much rated HP as they could. Just like OEMs recommendations to run at  ROP best power, which is right in the red box at 75-80F ROP, it seems they set up their max FF to provide every bit of  HP they could get out of the the engine rather than be concerned with longevity. But practicality really reigns here, if we're talking about a fire breathing 310 HP STC on the S/R or TN's these engines are already producing plenty enough power that they can be operated even extra rich to run a bit cooler - so what if they loose a few HP when they are already putting out over 300. But one wouldn't want to go to overboard on say a K with a 210 or 220 HP since going overly rich will rob the engine of power and the airframe is going too need virtually every pony. Of course when we're talking about max FF at takeoff, this discussion is limited to Continentals since Lyc are not field adjustable.

i assume when you talk about overly rich you might be switching to Idle mixture?  Its pretty rare to see an engine suffering from being overly rich at takeoff compared to overly lean. But we do see a few (more often in turbo's). Most shops and mechanics are rightfully paranoid about setting FF to far above TCM's spec. But its a universal issue in both Lyc's and Continentals to see an overly rich idle mixture. My theory is an engine will have a difficult time idling smoothly because of an induction leak and rather than fix the root issue, someone increases the mixture to make up for it. 

[Shadrach]

3 hours ago, kortopates said:

Ross, virtually the whole industry agrees Continentals are set up too lean at takeoff because of Continentals spec is on the lean side. Its a very accepted practice of adding a 0.5 to 1.0 GPH above Continentals high number when doing the set up. I can't say why Continental is a bit lean, but I've always assumed it was because they wanted to certify their engines with a much rated HP as they could. Just like OEMs recommendations to run at  ROP best power, which is right in the red box at 75-80F ROP, it seems they set up their max FF to provide every bit of  HP they could get out of the the engine rather than be concerned with longevity. But practicality really reigns here, if we're talking about a fire breathing 310 HP STC on the S/R or TN's these engines are already producing plenty enough power that they can be operated even extra rich to run a bit cooler - so what if they loose a few HP when they are already putting out over 300. But one wouldn't want to go to overboard on say a K with a 210 or 220 HP since going overly rich will rob the engine of power and the airframe is going too need virtually every pony. Of course when we're talking about max FF at takeoff, this discussion is limited to Continentals since Lyc are not field adjustable.

i assume when you talk about overly rich you might be switching to Idle mixture?  Its pretty rare to see an engine suffering from being overly rich at takeoff compared to overly lean. But we do see a few (more often in turbo's). Most shops and mechanics are rightfully paranoid about setting FF to far above TCM's spec. But its a universal issue in both Lyc's and Continentals to see an overly rich idle mixture. My theory is an engine will have a difficult time idling smoothly because of an induction leak and rather than fix the root issue, someone increases the mixture to make up for it. 

I misread your statement.  I had it in my mind that you were stating that most turbo'd Continental Mooneys needed their fuel systems gone over because they were typically set up too rich max power and that you were suggesting that this pilot's incident was caused by over rich condition when the throttle was advanced.  

[kortopates]

3 hours ago, Shadrach said:

I misread your statement.  I had it in my mind that you were stating that most turbo'd Continental Mooneys needed their fuel systems gone over because they were typically set up too rich max power and that you were suggesting that this pilot's incident was caused by over rich condition when the throttle was advanced.  

no worries, sorry if I wasn't clear. But I was referring to overly rich idle mixture when from when he pulled it back to idle for landing.

[N201MKTurbo]

1 hour ago, kortopates said:

no worries, sorry if I wasn't clear. But I was referring to overly rich idle mixture when from when he pulled it back to idle for landing.

FWIW

I spoke to the owner of the Rocket I was flying.

Sometime between the first low speed fuel flow adjustment and when it started working properly, the fuel pump was replaced.

[peevee]

23 hours ago, N201MKTurbo said:

FWIW

I spoke to the owner of the Rocket I was flying.

Sometime between the first low speed fuel flow adjustment and when it started working properly, the fuel pump was replaced.

the rocket we had was the same way, sounded and felt like a 60's muscle car with a huge cam.

I did not increase fuel with it on descent, at the reduced power settings it was fine, sometimes it would have to be leaned more in the pattern to run smooth, you just had to be really careful going around or it might cough on you and decide not to power up.

rocket has to be set up per the rocket manual, if it's set up per the cessna 340/414 fuel settings it's too rich, or so I've been told by a couple shops.

we had both our engine driven and boost pump overhauled, no change for us. Boost pump was the original from the 70's, doesn't get much use with the continental engine I guess.

 

maxwell said the stumble was normal. I've flown two rockets, one did it, one didn't. I tend to believe it is an abnormal situation.

Edited August 29, 2018 by peevee

[peevee]

On 8/26/2018 at 12:48 PM, kortopates said:

We've talked about mixture on final many times here with a number of people saying they need to avoid going full rich mixture because of the very thing this pilot confronted. That is fine for those of you experienced enough and well practiced to go rich on the go. But I've also tried to make the point in a few of these discussions that if one really needs to do this that this means the fuel system is not set up properly with respect to the idle mixture adjustment and should be addressed. Although the NTSB didn't get to follow through and verify this, I bet they would have found an overly rich idle mixture is what got this pilot into trouble.

 

With a NA engine, definitely avoid full rich at altitude.

With a T/TN engine as in the case? I agree, with proper setup it should be full rich.