High DA Engine died on rollout otherwise awesome 617nm flight!

[Ragsf15e]

Fun flight today! 617nm, KSFF to KMMH (Eastern Washington to Central Calif), fully loaded with wife, two kids, maybe 50lbs below mgw with 58gallons of fuel.  Still landed with ~18!  First time running a tank dry too… watched for the pressure to drop and caught it without even a stumble - thanks MS!

Weird thing for me though… density altitude was very high on landing.  Say 9500’.  I didn’t go full rich in the pattern but maybe 1/2” from it.  On rollout the engine died.  Wife and kids were a little freaked out but I’ve heard that can happen.  Was a little embarrassing (although I had enough smash to roll off the runway and turn onto the ramp).  The fbo called on ctaf and said, “when you get the engine started, follow the golf cart to your parking spot.”  Thanks for noticing . Thankfully the engine started relatively easily.

So what happened?  Throttle all the way closed, too rich, flooded it is my guess?

[EricJ]

19 minutes ago, Ragsf15e said:

Fun flight today! 617nm, KSFF to KMMH (Eastern Washington to Central Calif), fully loaded with wife, two kids, maybe 50lbs below mgw with 58gallons of fuel.  Still landed with ~18!  First time running a tank dry too… watched for the pressure to drop and caught it without even a stumble - thanks MS!

Weird thing for me though… density altitude was very high on landing.  Say 9500’.  I didn’t go full rich in the pattern but maybe 1/2” from it.  On rollout the engine died.  Wife and kids were a little freaked out but I’ve heard that can happen.  Was a little embarrassing (although I had enough smash to roll off the runway and turn onto the ramp).  The fbo called on ctaf and said, “when you get the engine started, follow the golf cart to your parking spot.”  Thanks for noticing . Thankfully the engine started relatively easily.

So what happened?  Throttle all the way closed, too rich, flooded it is my guess?

This just came up in another thread, that setting the idle rpm low (like many of us do), may not be high enough to keep it running at high DA.    If it works fine again at lower DA, just try to remember to keep a little throttle on rollout, or crank the idle rpm a little higher.

[Ragsf15e]

2 minutes ago, EricJ said:

This just came up in another thread, that setting the idle rpm low (like many of us do), may not be high enough to keep it running at high DA.    If it works fine again at lower DA, just try to remember to keep a little throttle on rollout, or crank the idle rpm a little higher.

Thanks.  I guess I missed the part about high DA in the other thread, but I remembered you guys saying yours idles ~600… I actually checked mine at home today before takeoff and it was at 500-550!  It ran ok there for a second and I just thought my surefly was awesome!  Well apparently that high DA thing is real.

[EricJ]

39 minutes ago, Ragsf15e said:

Thanks.  I guess I missed the part about high DA in the other thread, but I remembered you guys saying yours idles ~600… I actually checked mine at home today before takeoff and it was at 500-550!  It ran ok there for a second and I just thought my surefly was awesome!  Well apparently that high DA thing is real.

That's about where I keep mine, but it does increase susceptibility to issues at high DA, which I do fly in here in the summer.   So far mine hasn't quit, but it's probably in my future.      One difference might be that I rarely go to full rich on landing, especially at altitude, so that may help.

So you get to choose between more than necessary float on landing, or increased chance of it quitting on rollout at high DA.    It's why we get the big bucks! 

 

[MikeOH]

I've not landed at a 9500 DA, highest was at Big Bear, L35, at around 8500 DA.  I had the mixture much leaner than 1/2" from full rich and didn't have a problem on roll out.  Mine idles at closer to 650-700; so, there's that.

I based my landing mixture setting on previous similar high DA history where that's where it was when leaned for TO power (based on achieving sea level WOT EGT) figuring that's where I'd want it if I needed to go around.

[donkaye]

7 hours ago, Ragsf15e said:

Fun flight today! 617nm, KSFF to KMMH (Eastern Washington to Central Calif), fully loaded with wife, two kids, maybe 50lbs below mgw with 58gallons of fuel.  Still landed with ~18!  First time running a tank dry too… watched for the pressure to drop and caught it without even a stumble - thanks MS!

Weird thing for me though… density altitude was very high on landing.  Say 9500’.  I didn’t go full rich in the pattern but maybe 1/2” from it.  On rollout the engine died.  Wife and kids were a little freaked out but I’ve heard that can happen.  Was a little embarrassing (although I had enough smash to roll off the runway and turn onto the ramp).  The fbo called on ctaf and said, “when you get the engine started, follow the golf cart to your parking spot.”  Thanks for noticing . Thankfully the engine started relatively easily.

So what happened?  Throttle all the way closed, too rich, flooded it is my guess?

If you're flying at 9,500 feet, where is the mixture control?  That's where it should be when you're landing at 9,500 DA.  My educated guess is that you landed with a mixture that was too rich.  Starting at high DA also requires a lean mixture.

Even with turbocharged engines you need to land with a lean mixture.  Starting a turbo at high density altitude requires a lean mixture.  Taxiing both turbo and NA engines require a lean mixture on start and taxi.  Takeoff at high DA as you know requires leaning on an NA engine.  Takeoff with a turbo engine at high DA requires a static takeoff because you need to nurse both the power and mixture in until you have full power.  I've taken off with DA at 13,500 at Leadville using that technique.

If you have trouble starting at high DA, wait between tries, if you haven't gotten the mixture just right.  Remember the air is really less dense and that means lack of cooling for the starter.  Imagine burning out a starter at an airport like Leadville.  I learned that lesson many, many years ago at Leadville while teaching the Mountain Flying class, when I let the student crank too long.

[midlifeflyer]

2 hours ago, donkaye said:

If you're flying at 9,500 feet, where is the mixture control?  That's where it should be when you're landing at 9,500 DA.  My educated guess is that you landed with a mixture that was too rich.  Starting at high DA also requires a lean mixture.

 

Having seen it a number of times over the course of 20 years in Colorado, my guess is exactly the same as yours. 

 

9 hours ago, Ragsf15e said:

I didn’t go full rich in the pattern but maybe 1/2” from it

Waaaaay too rich at that D-Alt.

[Ragsf15e]

7 hours ago, donkaye said:

If you're flying at 9,500 feet, where is the mixture control?  That's where it should be when you're landing at 9,500 DA.  My educated guess is that you landed with a mixture that was too rich.  Starting at high DA also requires a lean mixture.

Even with turbocharged engines you need to land with a lean mixture.  Starting a turbo at high density altitude requires a lean mixture.  Taxiing both turbo and NA engines require a lean mixture on start and taxi.  Takeoff at high DA as you know requires leaning on an NA engine.  Takeoff with a turbo engine at high DA requires a static takeoff because you need to nurse both the power and mixture in until you have full power.  I've taken off with DA at 13,500 at Leadville using that technique.

If you have trouble starting at high DA, wait between tries, if you haven't gotten the mixture just right.  Remember the air is really less dense and that means lack of cooling for the starter.  Imagine burning out a starter at an airport like Leadville.  I learned that lesson many, many years ago at Leadville while teaching the Mountain Flying class, when I let the student crank too long.

I agree it needed to be leaner on landing, however, i cruised lean of peak and left it there during descent.  That works fine during the descent and lower power entering the pattern, but it needs to be set richer (not as much as i did) to set up for max power in case of a go around.  If i just left the mixture at cruise setting it would be much too lean if I tried to go around.  Hard thing is having a better guess for the optimum full power position that high.  I agree I probably was way too rich but don’t have a way to set it perfectly in the pattern without going full power and setting target egt like on takeoff/climbout.

[EricJ]

51 minutes ago, Ragsf15e said:

I agree it needed to be leaner on landing, however, i cruised lean of peak and left it there during descent.  That works fine during the descent and lower power entering the pattern, but it needs to be set richer (not as much as i did) to set up for max power in case of a go around.  If i just left the mixture at cruise setting it would be much too lean if I tried to go around.  Hard thing is having a better guess for the optimum full power position that high.  I agree I probably was way too rich but don’t have a way to set it perfectly in the pattern without going full power and setting target egt like on takeoff/climbout.

One way around that is to descend under power.    Leave the power high, trade the altitude for airspeed, and creep the mixture richer as you descend as needed.   Then when you're at or near pattern altitude the mixture will be close to where it needs to be if you need to go around.    I haven't had it quit on the ground at high DA doing it this way, but maybe I'm just lucky.

You do have to keep eye on EGTs, though, or it can get go lean under power quickly, and you may be cranking along faster than you like if it's bumpy out.    So it's a tradeoff, but it does give you an idea of where the mixture should be for the conditions.

[Ragsf15e]

11 minutes ago, EricJ said:

One way around that is to descend under power.    Leave the power high, trade the altitude for airspeed, and creep the mixture richer as you descend as needed.   Then when you're at or near pattern altitude the mixture will be close to where it needs to be if you need to go around.    I haven't had it quit on the ground at high DA doing it this way, but maybe I'm just lucky.

You do have to keep eye on EGTs, though, or it can get go lean under power quickly, and you may be cranking along faster than you like if it's bumpy out.    So it's a tradeoff, but it does give you an idea of where the mixture should be for the conditions.

I had it pulled back a bit because of the bumps, but usually I do descend under full power if it’s smooth although I don’t normally change the mixture until entering the pattern.  If I started LOP, and add a little through the descent, I guess I wouldn’t know exactly where im set?  If I don’t change mixture during descent it stays lop even though the servo is slowly increasing ff during the descent.

Do you start lop descent and then start adding a little mixture as you descend?

[EricJ]

2 minutes ago, Ragsf15e said:

I had it pulled back a bit because of the bumps, but usually I do descend under full power if it’s smooth although I don’t normally change the mixture until entering the pattern.  If I started LOP, and add a little through the descent, I guess I wouldn’t know exactly where im set?  If I don’t change mixture during descent it stays lop even though the servo is slowly increasing ff during the descent.

Do you start lop descent and then start adding a little mixture as you descend?

I'm usually cruising ROP, so I just adjust mixture as I descend.   If I'm LOP I'll bump it up to a typical ROP EGT and then descend...just to make the methodology consistent, no other reason.    Have to admit I don't remember trying cruising LOP and then just descending under power.

[PT20J]

It's not so much the mixture control but the throttle. If you set the idle speed low then at high density altitudes there isn't enough air at closed throttle. I used to go to KMMH a lot and I've had it quit on rollout until I learned to advance the throttle a bit after touchdown. You don't need to mess with the mixture because the mixture control isn't really in the picture at idle unless you pull it waaaaay back.

The RSA fuel injector normally meters fuel to match airflow using the pressure difference between the venturi and the impact tubes. But at idle (and near idle) there is not enough airflow to meter properly. So, at idle, the mixture is set by a linkage connected to the throttle that opens a valve at the main jet as the throttle is opened. After the throttle opened to maybe 1000-1200 rpm, the valve is fully open and there is enough airflow for the servo to meter normally. Since the idle mixture is controlled by the throttle position, and not actual airflow, it will be off optimum at density altitudes different from where it was set.

By the way, understanding how this works is why I quit ground leaning. If you lean it enough to just barely idle, the engine won't accelerate enough to taxi. And, if you lean it so you can taxi, the mixture control isn't really doing much of anything at lower rpms because the mixture is being controlled by the throttle. So, for ground leaning on an RSA fuel injected engine to be very effective, you really need to change the mixture control every time you move the throttle. I haven't ground leaned for a long time and I never foul plugs. But Ross is probably the only one that will agree with me because ground leaning has become another "must do" thing. 

[flyboy0681]

10 hours ago, donkaye said:

If you're flying at 9,500 feet, where is the mixture control?  That's where it should be when you're landing at 9,500 DA.  My educated guess is that you landed with a mixture that was too rich.  Starting at high DA also requires a lean mixture.

Even with turbocharged engines you need to land with a lean mixture.  Starting a turbo at high density altitude requires a lean mixture.  Taxiing both turbo and NA engines require a lean mixture on start and taxi.  Takeoff at high DA as you know requires leaning on an NA engine.  Takeoff with a turbo engine at high DA requires a static takeoff because you need to nurse both the power and mixture in until you have full power.  I've taken off with DA at 13,500 at Leadville using that technique.

If you have trouble starting at high DA, wait between tries, if you haven't gotten the mixture just right.  Remember the air is really less dense and that means lack of cooling for the starter.  Imagine burning out a starter at an airport like Leadville.  I learned that lesson many, many years ago at Leadville while teaching the Mountain Flying class, when I let the student crank too long.

Just made a pilgrimage to Leadville last week (by car). Quite a place.

[N201MKTurbo]

So, your engine died. The remark from the line guys probably wasn’t snarky. You got to figure it happens all the time. It’s not just you. 
 

You could spend a half hour futzing with the idle speed and mixture at that airport and get it to work reliably, but then it would be iffy at the lower elevation airports. 
 

The minor inconvenience once in a blue moon isn’t that big a deal. Just restart the engine and enjoy your trip.

[PT20J]

37 minutes ago, flyboy0681 said:

Just made a pilgrimage to Leadville last week (by car). Quite a place.

You should fly in sometime in the morning before it gets hot. I did it years ago solo in a J. It's in a big valley. There's a flight school there. How cool would it be to solo at the highest airport in North America? The FBO used to sell T-shirts -- maybe they still do. When I was there, two Army Hueys landed and the pilot's bought T-shirts.

[N201MKTurbo]

I have landed there about 4 times. All in my M20F. Never any issues landing or taking off. The runway is long enough to land the Space Shuttle. It is flat for about 5 miles is all directions. 
 

It is harder getting into the valley, than landing or taking off.

[Ragsf15e]

3 hours ago, PT20J said:

It's not so much the mixture control but the throttle. If you set the idle speed low then at high density altitudes there isn't enough air at closed throttle. I used to go to KMMH a lot and I've had it quit on rollout until I learned to advance the throttle a bit after touchdown. You don't need to mess with the mixture because the mixture control isn't really in the picture at idle unless you pull it waaaaay back.

The RSA fuel injector normally meters fuel to match airflow using the pressure difference between the venturi and the impact tubes. But at idle (and near idle) there is not enough airflow to meter properly. So, at idle, the mixture is set by a linkage connected to the throttle that opens a valve at the main jet as the throttle is opened. After the throttle opened to maybe 1000-1200 rpm, the valve is fully open and there is enough airflow for the servo to meter normally. Since the idle mixture is controlled by the throttle position, and not actual airflow, it will be off optimum at density altitudes different from where it was set.

By the way, understanding how this works is why I quit ground leaning. If you lean it enough to just barely idle, the engine won't accelerate enough to taxi. And, if you lean it so you can taxi, the mixture control isn't really doing much of anything at lower rpms because the mixture is being controlled by the throttle. So, for ground leaning on an RSA fuel injected engine to be very effective, you really need to change the mixture control every time you move the throttle. I haven't ground leaned for a long time and I never foul plugs. But Ross is probably the only one that will agree with me because ground leaning has become another "must do" thing. 

Thanks, that helped a lot.

[dkkim73]

Funny I have a lean ish idle mixture after recent engine work which is great up here but the engine died with even modest ground leaning in the swampy lowlands (1250 MSL, Wenatchee, Rags's stomping grounds )

Had quitting on roll out before the fuel work but some of that was attributed to low unmetered idle fuel pressure by some knowledgeable Mooney mechanics. Probably unrelated here (sounds too rich in Rags's case as Don explained better). 

On the descent leaning issue... I've been doing incremental MP changes and tried to follow with mixture according to TIT, and finally going to the rich side on the initial segment (or entering the pattern), targeting some reference such as 1450TIT.

I do feel like the descent leaning guidance is a bit diffuse compared to other guidance. 

 

 

[flyboy0681]

6 hours ago, PT20J said:

You should fly in sometime in the morning before it gets hot. I did it years ago solo in a J. It's in a big valley. There's a flight school there. How cool would it be to solo at the highest airport in North America? The FBO used to sell T-shirts -- maybe they still do. When I was there, two Army Hueys landed and the pilot's bought T-shirts.

Leadville is on my list for the transcon trip I’d like to make. And yes, they still sell T shirts as well as a lot of other merchandise. 

[donkaye]

Returning from teaching at the MAPA PPP Mountain Flying Class in 1996 with my Mentor Instructor Bob Goldin, the best Instructor I have ever had the privilege of flying with.   I try to carry on my teaching with the wisdom he instilled in me.

[N201MKTurbo]

So how high is Leadville 9927 or 9934. The shirt and building say 9927 and the sign says 9934. Humm…

[midlifeflyer]

9 hours ago, dkkim73 said:

I do feel like the descent leaning guidance is a bit diffuse compared to other guidance. 

It is. You are either going to use enough power to get a read on leaning during descent or you are going to guesstimate it. I’ve always guesstimated but that’s because I lived there and I knew what the takeoff lean setting looked like.
 

But for the transient (who is far more likely to be too rich than too lean) let’s bear in mind what our manuals say about leaning for takeoff. They vary. Some say nothing, but most talk about 3000’.  Not that it’s gospel, but it gives an idea of the size of the ballpark.  It also suggests that smooth engine operation at 3000 AGL, perhaps with an enruchening twist or two of the mixture vernier will be enough for go-around needs (although one must b read to tweak).