This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
Instructor’s Narrative
The flight was for takeoff and landings in the traffic pattern. We were on about the fifth lap in the pattern on the downwind leg. Abeam of our landing point the student adjusted power, put in 10° of flaps, and turned carb heat on.
I noticed the student then added throttle a few seconds later, but I observed no change in engine sound, felt power, or RPM.
I took control of the Cessna 172 and added power and observed no change.
I immediately turned towards the runway and checked the ignition switch, the carb heat, and fuel selector valve.
At this point I was convinced my engine had failed and I requested priority handling. I was given landing clearance for Runway XX. I continued my short approach to the runway and figured out that by pulsing the power the engine would give me very small bursts of power. I continued to do this in order to extend my glide. The landing was normal.
By continuing to pulse the power, I was able to taxi to the edge of the ramp, where the engine then shut off.
After the engine shut off I removed my hand from the throttle and observed the knob was out several inches towards “lean.”
We checked our fuel quantity and observed the plane still had 14 gallons on board.
I pushed the mixture knob in to “rich” and attempted to restart the engine. It restarted and ran normally.
My conclusion is that the student accidentally leaned the mixture while attempting to adjust carb heat, power, and flaps while abeam the landing point. Since I reached for the throttle when I observed the issue, my view of the mixture knob was obscured, and I failed to notice it in the lean position.
Due to this and the limited time to trouble shoot from 1,000 AGL, I treated it as an engine failure and executed an immediate landing.
In any future event I will be sure to double check the mixture in the event of an abnormal engine event. Additionally, I will stress the importance of adjusting the correct thing while performing the before landing checklist.
Also, I will stress the importance of verbalizing any abnormal that the student may observe so that the maximum amount of time possible is available to troubleshoot.
Student’s Narrative
I am a student who has 10 hours of total flight time. I was working touch and goes at the ZZZ airport.
At the beginning of my base turn I opened up 10° of flaps, put on carb heat, and reduced power.
I believe that by accident instead of pulling the carb heat I leaned the fuel mixture to the engine. This led to the engine to turn off and my CFI had to make an immediate landing.
My CFI did a great job of taking over the controls and getting us safely down on the runway. Nobody was injured due to this mistake.
Primary Problem: Human Factors
ACN: 1949940
Any engine hiccup, it’s FUEL, FUEL, FUEL! (THROTTLE, MIXTURE & TANKS) then IGNITION. You need Fuel,Air & Spark to keep the cylinders happy!
I might have to land off the airport someday but not if the engine quits “abeam the touch down point.”
I often times pull the power to idle abeam the numbers and NEVER have a problem easily making it to the runway.
That should be practiced occasionally. IMHO.
Will we go for day four on this story? Shouldn’t mixture have been checked pretty much right away?
Why has this same story been posted at least three straight days??
I wondered the same. And it has been posted in another aviation related site, also.
Engine controls are identifiable by feel, as they’re different shapes! It’s even mandated in the FAR!
Different shapes and colors!
Regardless of checklist or not, the knobs on carb heat and mixture are different colors and have different action, at least on all the 172s I had the pleasure of flying. The carb-heat just slides in and out. The mixture has a button on the end that must be pushed in to move the control in and out, and turning the knob allows for more precise positioning. I don’t think I ever tried yanking the mixture to know if it would work that way, but if it does, I’d expect a ratcheting feel and noise when yanked.
Far, far superior way to address fuel mixture adjustment issues is how Rotax does it with their CV(Constant Velocity) carburetors installed on their 914 powerplants. These have been highly successful standard equipment on all Japanese street motorcycles like Honda, etc. from the late 1960’s. You simply have on the top of the carburetor a vacuum diaphragm maintaining proper fuel mixture by controlling the vertical slide/tapered needle position in the carb main jet in fuel bowl below. No foo foo electronics/fuel injection/FADEC, or any electronics whatsoever. Too simple too easy. This should’ve been mandatory retrofit on all GA aircraft that essentially are using carb technology dating from the 1920’s.
The Bing CV carbs are interesting, but on the 912, two of them feed an 80 c.i. engine.
So, my GO-300 would need 6 of them, one for each of the 50 c.i. cylinders.
I can imaging the nightmare throttle linkage and the hours spent balancing the 6 carbs….
[ it took hours to balance the 4 carbs on my Honda 4 cylinder ].
BTW, the Bing carb is NOT immune to icing….per the ‘heavy’ maint. manual, section 73-00-10 page 6.
What ever happened to GUMPS on the downwind? Haven’t flown much in twenty years, but that was the easiest pre landing checklist in a 172. Also with only ten hours, what was the CFI doing instead of watching the student?
Hats off to the instructor and the student. They learned. They learned simulated engine failure, even if it wasn’t suppose to happen.
They flew that airplane and landed without incident. Could have panicked and spun it in. Could have attempted to restart and off field landing. Could have seen the mixture and pushed it in. They learned and I hope they both took to the air again that day. With a little grin and some words. I prefer carb heat, throttle, and mixture to be independent controls. Tools in the toolbox for conditions.
I agree with Kent. What happened to the response for loss of power, “Everything forward?”
I’ve never understood why to carb heat isn’t directly coupled to the throttle in the 172. I’m not aware of any condition where carb heat is not called for if the RPM is below 2000 (green arc). Simple mechanical fix.
Try it at a high density altitude airport, like Casa Grande in July, at 107 degrees….. the engine will quit from flooding.
A friend did that exact thing there, flooded the engine and had an engine fire.
It only burned the paint off the cowl. but grounded the aircraft for weeks.
‘know what to do and when to do it.!!!
It’s been well over thirty years of flying, but I still clearly remember as a student with my instructor in the 80’s I pulled the mixture instead of the throttle in the pattern at Bay Bridge Airport in Maryland. The engine stopped making noise and I quickly pushed that red knob back in. The engine came back to life.
My instructor growled at me. Literally. Growled.
It just doesn’t seem like that hard of an item to identify and correct.
And 6000+ hours later, it is always on my mind when I’m selecting anything (knob, lever, selector, whatever) to change in the aircraft.
GUMPS
Duh.
For half-$million bucks a copy (the price of two average houses) I expect fully automatic adjustments of these engine input controls. Here’s a case where ‘AI’ is probably justified (although I dislike it for other reasons). Manually setting carb icing and fuel/air mixture is exactly akin to adjusting the spark advance in the Ford Model-T with a lever located in the steering wheel hub. OK in 1923, utterly ridiculous in 2023.
Counting on someone else or something else is not a solution. Those fail too.
Agree with Mark S. With the variables of altitude, air density, best or most economical power settings for whatever conditions you have, that “smart” computer just isn’t as smart as we are (or should be). They will fail with no quick/time-sensitive recourse.
Lol. Rotax flyers would like to disagree. Redundant, reliable, and smarter-than-you FADEC is readily available. It’s a beautiful thing for both crew workload and efficient combustion.
Oh… I stand corrected.
Especially if you’re talking about that one certified Rotax engine model that is certified with a whopping 1200 hr tbo and a really compelling 140 hp that can’t power my complex/high performance aircraft.
You’re right… but I’m talking about go fast go high aircraft where air pressure and density altitude changes still haven’t been properly addressed and/or tested to a meaningful tbo.
The last Cessna 172 with a carb. was 1986, and has a carb heat control. the market price is a range of $50k to $100k+.
The ‘restart’ Cessna 172R is fuel injected, so no carb heat….but current prices are well over $100k.
Comparing a carb mixture control to the model T spark advance , is ‘apples and oranges ‘ comparison.
Do you demand AI to tune your car radio ?…gosh, you have to manually select the station..
Note that aircraft are designed for maximum reliability, not for convenience, or pilot preference.!
Well, here’s where we disagree. The aircraft mixture control and the Model-T spark advance are a direct apples-to-apples comparison. They both affect the basic function of an internal combustion engine. Hand cranking a Model-T with the spark left in the advanced position caused many a broken arm when one cylinder fired and ran the crankshaft backwards. The invention of the vacuum advance mechanism on the distributor removed any driver involvement with spark timing. Simple, elegant, cheap solution to a problem. Automatic aircraft carb heating and mixture control could be simply invented and offered as a retrofit kit on those airplanes with manual controls, but retaining the manuals as hard overrides. Point here is pilots have enough stress just safely piloting the flying machine without needing to consider the technical functions of the engine. It boggles my mind that these are operator considerations in 2023. Such manual adjustments recall barnstorming and flapper girls dancing to the Charleston.
Regards/J
Another: “At this point I was convinced my engine had failed and I requested priority handling.”
I don’t get it.
What don’t you get… the student (albeit he screwed up) felt that he lost power, so he did what he thought/felt was correct. He had a plan even though he was initially wrong, but at least he had a plan.
What I don’t get is the trend of “asking for priority” instead of declaring an emergency. The CFI was “convinced” his engine had failed…that pretty much qualifies as an emergency in any aircraft’s POH.
I don’t see how telling us he/she “requested priority handling” precludes the possibility of the instructor did declare an emergency.
Doesn’t saying “Mayday Mayday Mayday” automatically request priority handling? Or do you imagine the instructor keyed the mic and said
“ZZZ Tower, Cessna 123, I seem to have lost all forward thrust produced by my engine. I would respectfully like to ever so humbly request priority handling.”
Especially during pattern work, the mixture can become an item that’s out of sight out of mind. I saw that many instructors during closed traffic would leave the mixture in the full rich position so I knew there was a likelihood that their students may not be properly checking and positioning that control. When these flights reached the runway numbers abeam point, they would call out a check of the mixture, but the student would tap the control with his fingers and say ‘mixture’, and then go on to the next control.
When I did a stage check with that student, I would lean the mixture on the downwind without saying anything. This is the condition one would likely have had they been arriving from the enroute segment on a crosscountry. Sure enough, when the student started the prelanding checklist, he would tap the mixture, and say ‘mixture’, but wouldn’t move it to the full rich position for landing (near sea level airport). The trap they made for themselves would become immediately obvious and it was always a good lesson learned. As they say, they would look but not see. It may have been what happened here after the student inadvertently pulled the mixture control – they may have been conditioned to inadvertently overlook the mixture. But in addition, I’m sure this instructor realized that when there is a engine problem, you cannot leave out any items on the emergency restart checklist.
This would be why my instructor has drilled into my head to physically push on the end of the mixture control, even if it is “supposed to” be all the way in. Makes a lot more sense after your comment and the story above.
Proper training, the CFIs training, would’ve had the cfi checking the mixture first. If you learn your subject well, it doesn’t matter if the technology os ancient or not. Yes, we are flying airplanes that roll off the line at $500k for a trainer, with 60 year old engine technology, and yes the FAA is responsible for this, but the technology, or lack of it, is not responsible for the incident.
True the standard Emergency Check List had been followed the problem would have been resolved before declaring an Emergency.
“Ancient” technology hasn’t a thing to do with it. Proper operation has everything to do with it! “GUMP” would have caught this error in seconds!
You don’t apply part carb heat.
Didn’t we all learn that the correct procedure to restart an engine begins with MIXTURE RICH ? I can still hear my instructor’s reciting the mnemonic to me, from 1973!
On the other hand, what are we doing flying in airplanes in 2023 that use this ANCIENT technology. The (mogas-burning) Rotaxes and (diesel / Jet-A) burning Thielert and Austro engines all use FADEC. One control, just like a car. We are so backwards in this country.
Ancient tech because it doesn’t add thousands of components to fail. Yup, todays cars are constantly in the shop for electronic problems…that’s a fact.
yup.!! no batteries needed.!! just 2 control cables.
I teach a flow on downwind in Pipers and Cessnas. For Cessnas: Fuel on both, mixture full rich, carb heat on, ignition both, primer locked.
Fullest tank and Fuel pump on for Pipers.
It’s the third item on both the Cessna and Piper restart checklists (forth item on the Cessna fuel-injected model).