Engine failure

[azpilot]

I had my most interesting aviation experience happen to me this last weekend. I took a colleague from work on a one hour scenic flight. The flight was great, and we returned back to our home airport. Tower gave me right traffic for 4R at KCHD. I entered on the downwind, and set up a nice stabilized approach.

Once I was over the numbers, I reduced the power to idle and started to round out. The mains touched down, and then, as the nose was coming down, the propeller stopped spinning.

Tower called me on the radio and asked me to exit at the next taxi way, and I had to respond and let them know the engine had died, and that I would try to restart it. I was not able to get the engine restarted and called them back up. Tower called the airport and had them come tow the plane back in.

It turns out the idle set screw had 'fallen out' according to the email I got. I will be incorporating a check of the idle performance into my checklist moving forward.

The guy working the tower handled the whole situation like a pro. He had to shut down the runway I was on and redirect all the traffic to the parallel runway. You should hear the stress level in voice go up a bit, but he handled it very professionally.

 

[Timbeck2]

Glad it died when and where it died and you are safe and can reuse the airplane. I need to get up there to that diner for breakfast.

 

[ircphoenix]

Idle check should have been taught as part of your runup, no?

 

[MAKG1]

If the idle screw fell out, why didn't it restart part throttle?

The engine probably died as soon as you went to idle. But it didn't stop windmilling until you got real slow.

 

[Caramon13]

Idle check should have been taught as part of your runup, no?

Was just about to say the same thing. Every checklist I have used has a check idle step as part of the last steps in run up. Some even have a mixture check too (check cut off).

 

[WannFly]

Was just about to say the same thing. Every checklist I have used has a check idle step as part of the last steps in run up. Some even have a mixture check too (check cut off).

The mixture cut off and idle check is a part of the checklist, at least in the cessna checklist at my school

Sent from my SM-G935V using Tapatalk

 

[azpilot]

Idle check should have been taught as part of your runup, no?

No, I've never seen that on a checklist. However, I have incorporated that into my checklist now.

That's actually one of the main reasons I wanted to write about this. I wanted to make sure other pilots were aware of the need to do the idle check.

 

[Tantalum]

Idle check should have been taught as part of your runup, no?

Wondered the same thing. I suppose there is a potential that the idle screw could fall out in flight though

Does anyone "clear" their engines occasionally if they're descending idle? I rarely descend at idle as was taught against it (and have a JPI to monitor temps), but sometimes you need to come in a little steeper and I'll give the throttle a little juice now and then to make sure it's still alive

why didn't it restart part throttle?

I bet a hot engine that just been windmilling would be difficult to restart, would need to be clever with the mixture and prime to get it going again

 

[exncsurfer]

View attachment 52513

No, I've never seen that on a checklist. However, I have incorporated that into my checklist now.

That's actually one of the main reasons I wanted to write about this. I wanted to make sure other pilots were aware of the need to do the idle check.

I don't know what you're flying but looks like its step 12 in the runup (from a 172 POH):
.........
10. Throttle -- 1800 RPM.
a. Magnetos -- CHECK (RPM drop should not exceed 150
RPM on either magneto or 50 RPM differential between
magnetos).
b. Vacuum Gage -- CHECK.
c. Engine Instruments and Ammeter -- CHECK.
11. Annunciator Panel -- Ensure no annunciators are illuminated.
12. Throttle -- CHECK IDLE.
13. Throttle -- 1000 RPM or LESS.
14. Throttle Friction Lock -- ADJUST.
..........
But if something fell out or shook loose after the runup, you'd have the same problem.

 

[Hank S]

Wondered the same thing. I suppose there is a potential that the idle screw could fall out in flight though

Does anyone "clear" their engines occasionally if they're descending idle? I rarely descend at idle as was taught against it (and have a JPI to monitor temps), but sometimes you need to come in a little steeper and I'll give the throttle a little juice now and then to make sure it's still alive

I see the idle descent for short final. Coming down from altitude, I keep my cruise MP and EGT.

 

[WannFly]

My CFI regularly vrooms the engine when doing engine out training to ensure that fan keeps running when we want it to

Sent from my SM-G935V using Tapatalk

 

[MassPilot]

Every plane I've flown had "check idle" in the run-up checklist.

 

[1600vw]

If this was my airplane and it was only the idle set screw that controls how much idle RPM one has, this would have blue thread lock put on it. The blue thread lock allows for whatever it is used on to be removed. The red you will need heat to remove whatever this was applied to.

As to the comments about check idle. This set screw could work loose in flight from vibration. Lets just say for argument purposes that the mechanic just set this. When you do your run up the RPM could be just fine. Then after a 3 hr flight not so much. When doing maintenance on my HB if I found this screw easy to turn it would be repaired.

When I purchased my airplane I found when doing checks that the idle air bleed screw had play in the threads. With the engine running if you wiggled that screw and did not turn it the idle would change. The carb was replaced. I had some say I would have replaced the top throttle plate of the carb. I told them all the parts in that carb have the same age. Why not start over with new? Some don't seem to understand that passageways can become enlarged just by the passage of fuel over time.

So if this was your airplane would you just readjust the idle set screw or would you do more? IMHO just setting the set screw is not repairing anything. If it fell out once, it will fall out again. How I view maintenance. Others can do what they want.

Tony

 

[MassPilot]

Speaking of idle check during run-ups, years ago I was doing a run-up with my CFI and when I pulled the throttle to idle after the mag check the tach was showing around 900-950 RPM. Normally the RPM's would be about 600-650 at idle. My CFI pointed out that it would be a problem when landing and we scrubbed the flight. Turns out the plane was just out of maintenance and the mixture was rigged wrong. Good thing we did the idle check.

 

[azpilot]

Every plane I've flown had "check idle" in the run-up checklist.

I've never seen it on a checklist.

 

[mtuomi]

Before flying, I always go through a checklist and think "does this make sense". For example, the checklist I have for my C150 has "Fuel...On" in approach checklist. Absolute garbage.
I don't use a checklist on a runup, I know what I want to see, and idle is definitely one thing that needs checking.

 

[mtuomi]

I bet a hot engine that just been windmilling would be difficult to restart, would need to be clever with the mixture and prime to get it going again

You'd lose that bet. It fires right up when you introduce fuel.

 

[MAKG1]

If this was my airplane and it was only the idle set screw that controls how much idle RPM one has, this would have blue thread lock put on it. The blue thread lock allows for whatever it is used on to be removed. The red you will need heat to remove whatever this was applied to.

As to the comments about check idle. This set screw could work loose in flight from vibration. Lets just say for argument purposes that the mechanic just set this. When you do your run up the RPM could be just fine. Then after a 3 hr flight not so much. When doing maintenance on my HB if I found this screw easy to turn it would be repaired.

When I purchased my airplane I found when doing checks that the idle air bleed screw had play in the threads. With the engine running if you wiggled that screw and did not turn it the idle would change. The carb was replaced. I had some say I would have replaced the top throttle plate of the carb. I told them all the parts in that carb have the same age. Why not start over with new? Some don't seem to understand that passageways can become enlarged just by the passage of fuel over time.

So if this was your airplane would you just readjust the idle set screw or would you do more? IMHO just setting the set screw is not repairing anything. If it fell out once, it will fall out again. How I view maintenance. Others can do what they want.

Tony

It's a carburetor. Blue threadlocker isn't going to do anything but make blue stains on the carb body. Too much engine heat.

The usual method is to slightly "disturb" the threads, which can be undone by repeated adjustment. Or else use a jam nut if it's possible to fit one on it.

I've never seen enlarged passages in a carb from fuel flow. I've certainly seen them plugged with evaporation residue and other crap in the fuel that gets past the filter. And carburetors certainly do not wear everywhere evenly.

 

[Tantalum]

It fires right up when you introduce fuel.

I've never had a problem starting hot engines, but never tried one that has been windmilling for a while with a closed throttle and full rich mixture. The OP did mention that he was unable to restart the engine. Since it was the throttle that had an issue the engine likely kept receiving fuel while it was windmilling, but with the throttle plate closed that mixture was probably very rich. If the OP tried restarting with a normal procedure (full rich, etc.) I can see why it wouldn't work. I assume you'd want to use some kind of flooded engine procedure in that case, IE, mixture all the way lean, throttle full open, and crank until it kicks then add mixture and go to idle

Spit balling here, but from my experience and based on the OP saying he couldn't restart it seems like it became "over rich" while it windmilled and flooded the engine

 

[Tantalum]

idle is definitely one thing that needs checking

Many people take for granted that an idling engine runs... they tend to assume engines fail at or near full power during take off or something. But not having power when you suddenly need it for a go around, etc., can make for a very bad day. Always check that it runs at idle

 

[Checkout_my_Six]

or...go back to where it was running? Don't just assume it broke....keep trying.

 

[Dan Thomas]

It's a carburetor. Blue threadlocker isn't going to do anything but make blue stains on the carb body. Too much engine heat.

The usual method is to slightly "disturb" the threads, which can be undone by repeated adjustment. Or else use a jam nut if it's possible to fit one on it.

Anaerobic threadlockers take as much as 350°F to loosen them. Some actually get tougher with heat up to that point. The bigger problem with threadlocker on an idle screw is the debris that will crumble off next time it's adjusted or removed, and that crud could plug the tiny idle ports. The spring that's on that screw is enough to prevent movement, and if the spring is too short or tired or missing, problems will arise. And that's rare. Really rare.

 

[Dan Thomas]

Spit balling here, but from my experience and based on the OP saying he couldn't restart it seems like it became "over rich" while it windmilled and flooded the engine

The screw controls the fuel flow to the idle outlet ports. A missing screw lets air in, breaking the suction that draws the fuel to the ports, and the engine would starve, not flood.

 

[Dan Thomas]

That screw might have been in place at the runup, and fell out during the flight. Might not have shown up on an idle check. A runup is a check of the engine's condition at the time of the runup, just like a medical is a check of your body at the time of the medical. It doesn't guarantee that you won't drop dead of a stroke an hour later.

The idle check is one of those things that doesn't mean a lot to some folks. They'll do the runup,then close the throttle, and if it wants to die they just open the throttle a bit. Seen that many times on a flight-school ramp. They've accumulated carb ice in the warm-up and runup, and they simply don't recognize it.

 

[luvflyin]

Wondered the same thing. I suppose there is a potential that the idle screw could fall out in flight though

Does anyone "clear" their engines occasionally if they're descending idle? I rarely descend at idle as was taught against it (and have a JPI to monitor temps), but sometimes you need to come in a little steeper and I'll give the throttle a little juice now and then to make sure it's still alive


I bet a hot engine that just been windmilling would be difficult to restart, would need to be clever with the mixture and prime to get it going again

I clear the engine. Never really timed how often but it s probably every 30 seconds or so

 

[1600vw]

The screw controls the fuel flow to the idle outlet ports. A missing screw lets air in, breaking the suction that draws the fuel to the ports, and the engine would starve, not flood.

You are talking about an Idle air bleed screw. We are talking about a throttle set screw. This holds the throttle plate open to adjust how fast an engine runs. Your Idle air bleed screw adjust the mixture of air to fuel when idling. These are two different screws.

Tony

 

[1600vw]

Anaerobic threadlockers take as much as 350°F to loosen them. Some actually get tougher with heat up to that point. The bigger problem with threadlocker on an idle screw is the debris that will crumble off next time it's adjusted or removed, and that crud could plug the tiny idle ports. The spring that's on that screw is enough to prevent movement, and if the spring is too short or tired or missing, problems will arise. And that's rare. Really rare.

Again Idle air bleed screw and Idle set screws are to different screws. One sets the idle RPM speed and one sets the air fuel mixture when at idle.

You never ever put anything on the idle air bleed screw..NEVER

 

[Dan Thomas]

Again Idle air bleed screw and Idle set screws are to different screws. One sets the idle RPM speed and one sets the air fuel mixture when at idle.

Yes, I know that. I misread the OP's post. Sorry about that. Still, there should be a spring on the idle adjust screw.

 

[CC268]

Before flying, I always go through a checklist and think "does this make sense". For example, the checklist I have for my C150 has "Fuel...On" in approach checklist. Absolute garbage.
I don't use a checklist on a runup, I know what I want to see, and idle is definitely one thing that needs checking.

This is actually a good excercise...a lot of checklists are very inefficient in terms of their order of operations. One thing I did with my Cherokee checklist was make a new one...I went through it (kept almost all of the steps) but rearranged it to follow a flow from left to right. Also changed the order in which certain items were called out (like something called out in approach checklist that really could be in the descent checklist, etc).

 

[Cpt_Kirk]

Does anyone "clear" their engines occasionally if they're descending idle? I rarely descend at idle as was taught against it (and have a JPI to monitor temps), but sometimes you need to come in a little steeper and I'll give the throttle a little juice now and then to make sure it's still alive.

Why do you descend at idle?

You have a lot more control over your temps if you keep power on.

 

[mtuomi]

This is actually a good excercise...a lot of checklists are very inefficient in terms of their order of operations. One thing I did with my Cherokee checklist was make a new one...I went through it (kept almost all of the steps) but rearranged it to follow a flow from left to right. Also changed the order in which certain items were called out (like something called out in approach checklist that really could be in the descent checklist, etc).

Very true. I used my C150 checklist as an example. "Fuel - On" makes absolutely no sense. C150 has no fuel selector, it just has a fuel shutoff valve. The engine dies in a matter of seconds when you turn it off. Why the heck would anyone "check" that it's "on" (you never move it anyways unless you're on fire) in descend?
Also, just like you've noticed, some checklist writers seem to prefer the "zig-zag" method with flows.

 

[ragedracer1977]

Speaking of idle check during run-ups, years ago I was doing a run-up with my CFI and when I pulled the throttle to idle after the mag check the tach was showing around 900-950 RPM. Normally the RPM's would be about 600-650 at idle. My CFI pointed out that it would be a problem when landing and we scrubbed the flight. Turns out the plane was just out of maintenance and the mixture was rigged wrong. Good thing we did the idle check.

I actually had this happen to me in a rental plane. I ran the checklist and it said "Smooth idle over 575rpm". Well, it was a smooth idle over 575rpm... I was just in the pattern for touch and goes. I couldn't get the plane to land. I could get the wheels to touch the ground, but it was still flying. On the 3rd attempt, I finally realized what was wrong. At that point, I couldn't get the RPMs under about 1200. I ended up pulling the mixture and killing the engine. I'm not sure what exactly the issue was, but the maintenance guys said it was some sort of servo or something that went bad. Cessna 172R.

No one ever mentioned to me that a too high idle might not be the best thing to have when trying to land.

 

[MassPilot]

I actually had this happen to me in a rental plane. I ran the checklist and it said "Smooth idle over 575rpm". Well, it was a smooth idle over 575rpm... I was just in the pattern for touch and goes. I couldn't get the plane to land. I could get the wheels to touch the ground, but it was still flying. On the 3rd attempt, I finally realized what was wrong. At that point, I couldn't get the RPMs under about 1200. I ended up pulling the mixture and killing the engine. I'm not sure what exactly the issue was, but the maintenance guys said it was some sort of servo or something that went bad. Cessna 172R.

No one ever mentioned to me that a too high idle might not be the best thing to have when trying to land.

For me it was a rental C172SP which I think has the same engine but different prop.

 

[Tantalum]

Why do you descend at idle?

I don't usually, and never during the initial approach to the airport, but there are times in the pattern near or on final when it goes to idle. If it hangs out there for more than say 15 seconds I'll give it a little bump. I've always seen CFIs do this too on BFRs, training, checkouts, etc. I wasn't sure if it's a psychological thing, or if there actually is some legitimate reason why it should be done so

I agree, temps, and the overall descent itself is much more controlled carrying some power, and it keeps the oil pressure more in the middle of the green zone

 

[OkieAviator]

For you self righteous types - Straight from my 172N POH

Now that we've established that it's not on every checklist, it's also safe to assume not all CFI's teach it. In fact I've been up with maybe 10 CFI/CFIIs and never once have any of them asked me if I did an 'idle check'. Nor do I do specific check, but at some point during taxing I pull it to idle. The only time I really mess with it is at altitudes and I set my mixture to a point that I can idle and keep the engine running.

On checklists for single engine pistons I advocate taking your planes documentation and rewriting it into some type of flow checks. As an example I don't set my parking brake on runup as suggested by the POH or in reality the AFM or whatever they called them before POHs. Once you've been flying a plane for awhile you don't need an exhausted checklist as if you're flying an Airbus 380.

 

[jsstevens]

Since I just switched clubs and instructors...

In the old club where the main training plane (C-172C) was owned by the instructor, we ran the plane at 1000RPM on the ground, leaned. He was adamant about keeping the RPM up, and it taxied rather briskly. He was also adamant about using the brakes sparingly. Run up check was pretty much what the manual said, no specific idle check (and in fact, I just went back to 1000 RPM after the checks).

New club, new instructor (who doesn't own the planes) and a C-172P. He had me do an idle check post run-up. And kept telling me to slow down on taxi. I mentioned "I hate riding the brakes." He said you just have to. (He's not buying the brakes.)

Upon reflection, I think the idle test is a good idea and I'm adding it into my mental checklist...

John

 

[midcap]

My CFI from day one has always said check idle rpm, when starting the engine, then when running up the engine. That's two times the idle rpm is verified.

 

[MAKG1]

For you self righteous types - Straight from my 172N POH

Now that we've established that it's not on every checklist, it's also safe to assume not all CFI's teach it. In fact I've been up with maybe 10 CFI/CFIIs and never once have any of them asked me if I did an 'idle check'. Nor do I do specific check, but at some point during taxing I pull it to idle. The only time I really mess with it is at altitudes and I set my mixture to a point that I can idle and keep the engine running.

On checklists for single engine pistons I advocate taking your planes documentation and rewriting it into some type of flow checks. As an example I don't set my parking brake on runup as suggested by the POH or in reality the AFM or whatever they called them before POHs. Once you've been flying a plane for awhile you don't need an exhausted checklist as if you're flying an Airbus 380.

So, you just leave it at 1700 RPM until takeoff?

 

[Tantalum]

o, you just leave it at 1700 RPM until takeoff?

lol, I wondered the exact same thing reading that checklist. It's an oddly worded checklist and seems more like something that was handwritten at the club then what came with the plane. Would you really wait until after the runup to check the avionics master?

For what it's worth the 172N I fly has after "suction" to set the throttle back at 1,000 RPM, but every CFI has always been aggressive on the "check full idle" right after the runup

 

[OkieAviator]

So, you just leave it at 1700 RPM until takeoff?

Which is another example of why you can't blindly follow a checklist. Should also note this 172 doesn't have an avionics switch so for some that might confuse them when they can't find it.