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.
The Cessna 150 lost engine power while in cruise flight to a practice airport with less traffic.
The day’s plan of action for my commercial student in her flying club airplane was to practice procedures, specifically steep spirals to landing.
As an instructor, I’ve flown this model of aircraft for a few hundred hours. I practiced or taught more than 30 engine-out landings in the past few months in this aircraft.
Recently the weather had changed from mild temperatures to cold temps being in the 20s at night, so the aircraft would seem to start much differently than in the warmer temperatures. In the warmer temperatures the airplane would start and quickly be able to maintain 1,000 rpm, but when it was cold outside the airplane would cut off if you tried to bring it back to 1,000 rpm for idle after starting.
This was one possible warning flag that we missed and was attributed to the cold temps.
Another warning flag was on a previous flight a few weeks earlier. This happened with another student. The aircraft had a much different type of engine surge, which I’ll describe as mild, with only a 100 rpm drop. This lasted a few minutes while over an airport and then returned to normal.
Fuel samples from before the flight had a few drops of water. I witnessed and double checked to make sure no more water was coming from either tank. The fuel is also a mixture of auto fuel and 100LL. This aircraft has a STC for auto fuel and is used to keep the cost down for the club.
That first time the aircraft surged I attributed it to possibly water contamination. I reported this to the A&P and the club replaced the spark plugs. I ran the airplane again and it didn’t sound or feel right, so I reported it again to the A&P and he replaced one magneto after it failed the mag check. After replacing the magneto the airplane still didn’t sound perfect, but passed all checks on the ground. The airplane just felt different than in the summer.
While flying at roughly 4,200 AGL I noticed the engine was surging from 2,400 rpm to 1,000 rpm and each time the RPMs would surge the range was getting larger. For example the first time it was from 2,400 to 1,000, then 2,400 to 900, 2,200 to 700 and it lasted about 40 seconds until the engine died.
The oil pressure and engine temps were in the green. The airplane was full of fuel and in the on position.
After the engine quit, I told my commercial student to fly the airplane at best glide and point it to the airport while I ran the checklist. After running the checklist, the airplane still wouldn’t start.
At the completion of the checklist, I requested priority on frequency. After requesting priority twice within roughly 30 seconds, a controller got on the frequency and gave us a discrete frequency. His voice was hard to hear because someone else was stepping on him while trying to relay information. The controller assured us that he knew where we were and that he’d send services after touchdown.
My commercial student identified a field that look suitable to land. He maneuvered the aircraft in a position where we could better identify any possible hazards in our intended landing area.
Once we were close to 2,000 AGL, I asked if my student was comfortable with me taking the landing and agreed to allow me to take the off airport landing.
At 1,000 AGL, I took the controls. As I got the airplane on a downwind I noticed power lines running across the field we were going to land on, so I quickly maneuvered the airplane to an adjacent field. Once in position similar to a high final approach, I slipped the airplane and put full 40° of flaps to slow down our ground speed and use as much of the available 2,300 foot long field. The rows aligned with our makeshift landing strip helped with not damaging the aircraft. The surface was a little more bumpy than landing in a traditional grass strip.
The airplane didn’t sustain any damage and we walked away from the aircraft and called Approach with a number they provided us on a discrete frequency after landing. Approach gave us another number to call and we talked to someone who told us to call so they could better find us. We dropped a pin using an iPhone and provided our address.
CRM really played a key role in allowing us to run the checklist, get services on stand-by, and fly. Assigning duties and tasks made it easier to accomplish the goal at hand and that was to aviate, navigate, and communicate. Understanding what my student was capable of performing allowed me to delegate.
Still haven’t heard what caused the airplane to stop running, but the FAA rep didn’t find any water in the fuel or metal in the oil. The tanks were still three-quarters full.
The FAA rep and the owner started the airplane, but it didn’t sound great to either one of them. The A&P/owner stated that it was likely a carburetor with a stuck float.
I know the aircraft has an auto fuel STC and it’s possible the fuel was possibly tainted with ethanol fuel that maybe caused the float to stick.
This is only my theory, because the owner still hasn’t take the carburetor off the airplane.
Primary Problem: Aircraft
ACN: 2082668
At best it is a 47 year old airplane. It is either fuel.or spark for he reson it quit, and since it started on the ground it was not spark. So I like the gentleman who said he changed his carb. My vote would go for carb replacement.
As to the use of auto fuel, I have 30 years of flying singles and twins on auto fuel in the Canadian far north. On a plus 30C day, I always ran the engines to full power with brakes locked to ensure they made full power as vapor lock is a real possibility, but I only encountered it once, maintaining altitude until runway was in site.
As to alcohol, if taking a twin from a heated hanger to minus 20 -:30C, I routinely added alcohol based deicer, so I could change tanks when needed. I also never ran a tank dry in the winter, changing tanks early to ensure they would change. Many fuel valves are less than 1/4 inch at the slide valve so not much moisture required to lock them solid, a bit of deicer (alcohol) prevents that.
Alcohol in fuel becomes a problem only when left for a long period of time, as it has a tendency to absorb water vapor over time, the water dilutes the alcohol lowering the octane rating. It can also destroy some fuel system parts, so it is necessary to understand what is in your systems. All these are some of the reasons auto fuel with alcohol has been banned from use in aircraft.
I own and operate a 1970 Cessna 150 with the mogas stc. I have run the airplane since 2008 with ethanol free auto gas. I had the carb professionally overhauled when I first acquired the plane in 08. Auto gas has never concerned me as a safety issue. I consider the shelf life of auto fuel to be less than 100LL. With this in mind I have drained older fuel at the belly drain and ran it my car placing fresh fuel in the aircraft. I recently installed an MT101 belly drain which gives me a fourth place to sump fuel on preflight.The biggest performance improvement came with a 500 hour inspection being performed on the 2001 Bendix mags. The 150 has a terrible fuel cap design which encourages water to leak into the fuel if the aircraft is stored outside. Be aware that junk and water will remain in the fuel system until the MT101 belly drain sump is installed and used each preflight. This is because the belly sump is the true lowest part of the fuel system, not the gascolator/strainer. I love the 150 series of aircraft, I fly mine semi monthly and it is hangared.
I would never put ethanol in any of my equip let along a plane. I only use Chevron 94. I have too much respect for my rear end to use ethanol.
An Old Saying:
If it does not work right on the ground it is not likely to work any better in the air.
“Priority handling” request after a complete power failure: No!
“Mayday, Mayday, Mayday”: Yes! (gets maximum attention from ATC)
Results must vary. I’ve had a fleet of vehicles using ethanol fuel and many of them set for years without issue. But did seemingly have problems with one Briggs and Stratton, but not with the other four…go figure 🤔
After running non alcohol mogas in my O-300 powered 172 for 40 years I got in it one day and it simply wouldn’t fire at all.
A shot of prime got it to run for a second then die.
Multiple attempts failed.
Removed carb and sent it off and replaced it with new.
Problem solved.
I don’t attribute the problem to the fuel.
Or it wouldn’t take 40 years.
Sometimes mechanical things fail.
Marvel Schebler has issued a number of mandatory service bulletins, MSA-13, on the float assembly; replacing the brass float with a black float, which was replaced with the current ‘blue’ float.
The original brass float can rub on the side of the bowl and wear a hole, which will cause the float to sink, flooding the engine with fuel.
The ‘black’ float was found to absorb gas and sink too.
So, the new Blue float works ok-great. Just remember to adjust the float level per the M-S service instructions. [ available online as a free pdf ].
Never put alcohol (ethanol) in your aircraft!! One reason it absorbs water! It sinks to the bottom of the fuel system!!
In the ole days we could put in our automobile and drive it. The engine would spit and sputter until All the water was gone. Common sense doesn’t exist anymore.
Auto fuel with up to 15% ethanol is deadly to carburetors. Ethanol acts as sugar caramelizing the inflow spigot. The same thing happens to your chainsaw and lawnmower engine.
I myself accidentally put ethanol tainted fuel in my 182 quite a bit of it after flying a couple trips I was amazed at how much water I had to sump out of each wing it’s as if the ethanol actually sucked water out of the air into my tanks. After I realized what was happening I drained all of it out and filled with the proper fuel
The more experience I get, the more I trust my gut I instincts.
Auto fuel used with the STC must be non-ethanol!
My self I would not fly the plane until it was fix and ran right.