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.
On roughly a three-mile final I told my student to maintain altitude at 4,800 until on glide path as we were getting four red lights on the PAPI.
We descended to 4,700 and again I said “maintain altitude until we get two reds and two whites.” At this time, he said “I’m at full throttle.”
We were descending now at about 1,000 rpms with throttle full and losing about 500 feet per minute.
At this point I took control and told my student, “I think we are landing on the freeway.”
A few moments later and only about 100 feet off the ground I said to my student, “We are landing on the freeway.”
I jockeyed the throttle a couple times and the Cessna 150’s engine sputtered. Then I pushed the mixture to full rich and the engine sputtered back to life. We slowly climbed away from the freeway and returned to the airport without further incident.
As I turned onto final approach to the freeway, I noticed traffic ahead about 1,000 yards and traffic behind about 3/4 mile. We were luckily positioned as to not harm anyone else.
After landing we inspected the inside of the engine cowl to find a wrench lodged. A more thorough preflight by my student may have found the wrench. It was difficult to see after the flight when I was inspecting with an intention to find something amiss.
The mixture was not changed from the run-up until about to touch down on the freeway. It was set perfectly for field elevation where we took off and landed. So, the only thing I can think to cause the problem was the wrench lodged against something disturbing the mixture or throttle. I look forward to talking with the mechanic tomorrow to see what exactly the wrench was lodged against and if that was the problem.
Primary Problem: Human Factors
ACN: 2142516
Poor cowl designs are part of the problem. As previously mentioned, a Cessna 150’s cowl permits very limited visual access to the whole engine. All cowls should be hinged on both sides to promote full access (Beech Bonanzas have this feature).
As a student many decades ago, I built time in Piper Cheroke 140s which had hinges on both sides of the aluminum cowlings to promote a clear visual shot of the entire engine compartment.
Then I rented a Cherokee 180 which had a solid fiberglass cowling (aka–cracks down the road) with access being limited to the oil dipstick via a small door. My first reaction was the proverbial, WTF?
Removing this cowl via 4 latches would be awkward, time consuming and best done by 2 people. Result? Nobody bothers. Good job Piper on the Warrior with a two-sided hinge system. Bad job Piper on the Archer with no hinge system. One may say that the Warrior and previous 140s have 0320 engines requiring less room thus giving the opportunity for more real estate to have a two hinged cowl. The 180s have larger 0360 engines in them sacrificing the space for providing a 2 hinged cowl. But isn’t it curious that there is an STCd conversion available for the Warrior to replace the 0320 with an 0360 while retaining the original 2 hinged cowl? Ask me how I know—a good friend of mine had the conversion done to his Warrior with no required cowl replacement. In addition, the first Cherokee 180s produced in the early sixties had the same 2 hinged cowl that the 140s had. This changed to the one-piece fiberglass cowl with the C models in 1965. My only conclusion is the Piper marketing Department decided that the one-piece cowl is cooler looking than the 2 piece thus sacrificing good function for esthetics. This is similar to Cessna who stopped the square tail design in favor of the swept tail design. Wow man!! Looks like a jet now! But ask any square tailed Cessna pilot which design he/she prefers, and they will say “the square tail because of better performance”.
“…a more thorough preflight by my student may have found the wrench…” One might ask about a “more thorough preflight by” the instructor. Nothing in aviation is better than a second set of eyes (regardless of rank or position) and mutual support. Thrilled for a successful landing and lesson learned…congrats!
I never place a tool in top of the engine or baffles.! I put them on the tool cart or the floor, depending on what I’m working on.
My though is a wrench may lodge between a couple of spark plug wire, abrade the shields and cause 1 or 2 upper plug to stop firing.
But the engine should run well on 1 mag, unless the wrench is causing an upper plug to fire at the wrong time. that would cause a loss of power.
Some people just shouldn’t be working on Aircraft. People that do not have a mechanical appitude test before should never be granted a license. Attention to detail at all times is mandatory.
Mixture is part of GUMPS check. How can you have 1000 rpms with full throttle?
Henry is correct, you would never see this looking through the cowl door on a 150.
Reminds me of the scene in the old movie “Iron Eagle” where Lou Gossett says he is adjusting the mixture (before the canyon race) on a 150 while working through the cowl door.
Incoherent.
This is why I don’t like cowlings that only give you access to the oil cap.
Thorough preflights are necessary, yes, and are as much a part of flight training as the flight itself. But a wrench in the engine compartment? It could be detected if it was left on top of the cylinders, but it wouldn’t affect the mixture or throttle. To affect those engine controls, it would have to have somehow been left adjacent to the carburetor. This could never be seen on preflight even by opening the oil service door!
The very GOOD REASON for a mandatory tool BOX inventory by the mechanic/person with hands on the engine before rrelease aircraft for flight. Every tool in the tool box is in its place when done with the work. No EXCUSE!
Exactly why many places require all mechanics’ tool boxes be “shadowed”, like I had to do, so a missing tool can be seen at a glance. It is a pain to have to shadow your box, but this article shows why it’s necessary. I’m retired now but in the past, I thought that this would be a good gig for someone – travel around the country and shadow boxes for mechanics who are required to do it, but don’t want the bother, and especially if they are required to do it on their days off and not on company time. And it can easily take a day or more to complete a toolbox.