The International Cessna 170 Association

I'm the author of a series of clean romances set in Alaska with the pen name Cathryn Brown. I have a situation in a book and I'm trying to figure it out. (For background on me: I grew up in Alaska and have flown Cessna 150/152, 172, and my family owned a 177-RG. But it's been a long time since I've flown.)

I have a character flying his 170 and he loses communications and the engine stops. He makes an emergency landing on a remote strip - of which are many in Alaska - and the plane is able to be repaired within a couple of hours by a mechanic who flies in later. Is it realistic for a 170 to have this type of failure, what would cause that, and would it be something that could be fixed that quickly?

Thank you for your help. I tried going through three Cessna places on the phone today and the wouldn't help me. It seems they don't want to talk about why planes fail, which is understandable.

It takes three things to keep an internal combustion engine running. Fuel, air, and ignition. Well, we are blessed with plenty of fresh air here in Alaska, so that isn't generally a problem. Aircraft engines are equipped with two ignition systems just so that a failure of one system doesn't automatically cause the engine to quit running. So that leads us to fuel. Now, if some nefarious character in your story (Snidely Whiplash perhaps?) were to put a hand full of tundra moss, or slow dissolving moose nuggets, in each gas tank, things could get sticky in the fuel system. A situation that might not lead to an immediate engine failure but could certainly cause trouble somewhere down the trail. And could yet be corrected by your trusty mechanic in the bush.
This is of course a simplistic scenario which might be useful for your story. In reality though, more than a few forced landings have been the result of fuel contamination, so it's not a completely far fetched concept.
Please keep us posted on your book's publication. I have a few granddaughters who might well enjoy reading your stories.
Bill

Carburetor ice can cause an engine to run rough and eventually stop if the atmospheric conditions are conducive to icing (cool moist air, which there is an abundance in Alaska except in winter) and no action is taken to melt the ice. If the reason for not melting the carb ice is the carb heat control cable failed, the engine could eventually stop and would be a simple repair by a knowledgeable mechanic. He might not be able to fix the broken cable but any mechanic will have a roll of safety wire that could be McGiver-rigged to get the plane and pilot home where it can be repaired with a correct new cable.

Not to get too far-fectched here, but some other items which may or may not tie into other areas of the story in which you are building. Environmental conditions could play a part: low clouds and moisture causing ice build-ups, forcing a landing. A slow fuel leak causing fuel starvation (caused by any number of things: a loose fuel cap/gasket, a hose that has a leak. Vacuum pump failure causing a loss of vac pressure and making the vac-controlled gauges (artificial horizon, etc.) slowly become inoperable. Accidentally striking a log on a sandbar during the precautionary landing, damaging part of the landing gear (flat main tire perhaps? Sheared off a bolt on a brake caliber?). The good news for you is that a 170 generally only has "one" of everything: minimal instrumentation, a single comm, single nav, single generator (or alternator), single this and that ... so taking one or more out of service has a pretty measurable impact depending on how far you want to take it. I've heard stories - never experienced myself - of cylinder replacements in the field which could be done in a relatively short amount of time by an experienced mechanic, signs/symptoms of which could be gradual or catastrophic depending on how you want to portray them. Not sure how to tied a comm problem into a mechanical problem unless there is an electrical failure (I have had that in another plane), but that wouldn't cause the plane to stop flying.

I dunno, maybe something like this ... ?

"Again, he wiped the back of his hand across the stubble that had grown bothersome on his chin, pressed his head forward towards the windscreen so he could get a better look at the lowering clouds. He has flown in weather worse than this, he tells himself. Takes another sip of the acrid coffee in his traveling cup, not because he needs it but because it's still there. Nasty stuff, but it reminds him of the better times when that damned dog was still alive. Wisps of ragged clouds flash over and under the wingtips as the ceilings continue to lower the further he flies up the valley. Temps are hovering just above freezing which is his bigger concern. And he presses on.

"A cautious man and a practical man he continues his scan of the instrument panel in the methodical way that the old geezer pounded into his head those many years ago. God, he hated that guy but a fine pilot he was. A slight needle tick caught his attention on the last pass across the aging instruments but it wasn't until a few minutes later that he started piecing together the disparate bits of info that were staring him in the face - suction was low, lower than it should have been at these settings, and things just didn't feel right with the artificial horizon.

"Another wisp of cloud flashed by, he was in an out of it in a second. The ceilings were definitely dropping. The practical and cautious man sized up the situation and the math wasn't good: the weather was deteriorating and while he was instrument-certified he had no business taking a seventy-year-old plane into the freezing clouds with failing instruments. Better to sort this out on the ground than in the air. He scratched his chin with the back of his hand once again, then pulled back the power to turn back towards the sandbar he has just overflown.

"The wheels kissed the strewn rocks making up the majority of the sandbar and he executed the same beautiful landing he has done in hundreds of other locations on hundreds of other days before, because that's just the way he did things.

"And it would have been the perfect landing, were it not for the effin' moose that stepped in his way ..."


On a serious note, though - there are a lot of very wise folks in the association that can offer better advice than I could and probably have a ton of practical experience with field repairs. As you start to narrow down your story options, please post them out here and I bet you will have a lot of very helpful members willing to pressure-test them for you. I am impressed by your attention to detail and thank you in advance for taking time to research this.

I hope that you took my post in the light-hearted way it was meant to be. Happy to be of further service - and best of luck with your book!

EDIT: Ok, two things have bothered me here: first, you have experience flying Cessnas so I think you have a grasp on most of items suggested in terms of electrical, mechanical, fuel, etc. The 170 has a very common 145-hp engine that is used in many early-model 172 and there is nothing overly unique about it to the 170, same with the airframe. The vacuum system is venturi-driven rather than a vacuum pump, so some options there for you, but again it's not going to make the plane fall out of the sky. Other posters have some excellent ideas which are non- 170-specific so you should find some really good add'l details out there on the web as you flesh this out. The second thing to note, is that with the limited info you provided I assumed it was "me" in the left seat, and thus wrote as if the pilot was a male. Please don't assume a gender-bias in my answer, as the pilot could be female or male, equally.

Not from Alaska, I have no idea how spotty communication might be. My first impression was your character had a communication malfunction. This could be as simple as a broken wire in a headset mic or a push to talk switch. Both could stop communication if there was no back up in the aircraft. And both a believable situation.

The engine completely stopping AND then being repaired at a remote strip a few hours later is a little trickier to handle. Easier explained is a malfunction causing partial engine power loss, but not stopped. The fuel contamination or carb ice scenario fits this better.

Another scenario that might work better is one in which the pilot realizes a malfunction had taken place that would cause imminent engine failure but he lands before the engine is destroyed. One very believable scenario that could be fixed in a few hours is the failure of the oil pressure indicator line. A failure of this line will cause all the oil in the engine to be pumped over board fairly quickly leading to catastrophic engine failure. If your character's oil pressure line broke in that portion of the line in the cabin, they would notice it very quickly and take immediate action as the hot oil would/could be spraying on their feet. Granted the oil line is more likely to break at the engine connection and the pilot would only know immediately, if he happened to serendipitously look at his oil pressure gauge which would be reading 0.

Good luck with your book.

Good scenario with the oil pressure line, Bruce. As you probably know, this exact scenario happened to Cleo Bickford on the way home from the Fairbanks convention in 1988. He landed on an emergency strip somewhere in BC and was able to make a temporary repair with a piece of hose and a couple of hose clamps he happened to be carrying.

What came to my mind was something that has happened to me. An exhaust valve stuck open, causing the engine to run rough, and only develop partial power. After a precautionary landing I was able to find the offending cylinder by touch - it was significantly cooler than the rest. A mechanic at the airport I landed at removed the top spark plug from the cold cylinder, turned the prop until the piston was at the bottom of the stroke, filled the cylinder w8th a length of rope, then turned the prop, causing the rope to push the valve closed. Several repeats of this process cleaned the valve stem sufficiently that it would close on its own.

You can get all kinds of ideas by reviewing NTSB reports and Kathryn's Report but I think it would be easier to subcontract Brian to write this scene for you. He's the next Ernest Gann!

WHOO HOOO, Way to go MILES!
I was reading thru this and wondering WHEN WILL ONE OF US MENTION A STUCK VALVE and the mechanic shows up and does the ROPE TRICK! ???

That is a believable and not-all-that uncommon scenario. Loss of communication in mountains is believable. A stuck valve is a violent shaking of the engine and instrument panel that is VERY unnerving and cause for an immediate precautionary landing. The ROPE TRICK (removing a spark plug, stuffing rope into the cylinder and then rotating the prop slowly pushes the piston up in the cylinder, compressing the rope and thereby pushing the stuck-open valve back into position and freeing it up, making the engine run again just fine) can be done by the mechanic OR by a knowlegeable pilot.

Then there’s an actual similarity that did occur to me (fellow coworker actually) while flying pipeline patrol in younger days: The pleated paper air filter became clogged with water and/or ice and the engine power was so reduced as to force a landing. That problem could be solved by cleaning or removing the filter.

I hate to carry this thread in the wrong direction, but , I had a situation a few years ago. Was taxiing out for take off at Kansas City International when I had a valve stick. Fortunately there was no big iron in back of me and the kind controller let me spin around and go back to the GA FBO. I found the offending cylinder by the touch method (cooler number 4). Had wrenches but no rope. Pulled the top plug and very carefully inserted a flat blade screwdriver between the top of the piston and exhaust valve. Did not take much pressure to pop valve back closed. Pulled it through a couple times and it didn't stick again. Took off and had an uneventful flight back home. (Was picking up my Mother-in-law at the airport, she did fly with me again ....)

Shannon B

You recognized a good source - It is apparent that many C170 Pilots have a Book in our hearts.

The oil pressure line breaking near engine block is a real mysterious item. The copper line ages, vibration etc . Fractures after excess hours in service. Extremely rare, but you want mystery in plot.

Here is two (2) more situations to consider..

Engine suddenly stops W/O exhibiting symptoms - Potential cause - aged gasket on Gascolator - fails - air is sucked in - acts like embolism in an artery. Stops fuel flow.

Comm failure -- very old radios - connector is 1-1/8 dia. - These connectors are tied together with cotton twine (1953), no poly. Airplane has been flown in rough windy conditions - cotton twine deteriorated years ago now connection has been separated. communication has been lost.

Tell us the romance plot in your novel.

Losing communication and an engine failure at the same time seems a bit far fetched to me. One way to get around this is to have some other pilot/aircraft with a stuck mic rendering that frequency inop. 30+ years ago a friend and I flew a rented Comanche to LAX. The ground controller at LAX was not amused when we had a stuck mic on his frequency.

MoonlightVFR wrote:... - These connectors are tied together with cotton twine (1953), no poly.

Or flax/linen, and rayon (in use since the first world war)

Thank you for your help! This is exactly what I needed.
It looks like I have options for the engine failure. In the story, they need to make an emergency landing and not be able to call for help. They're going to be together for a couple of days in the Alaska wilderness until they get help. (In a Hallmark movie, clean romance way. If the radio doesn't go out too, then he would be able to get help faster. I don't want that. I'm still working on why the ELT failed, but it looks like isn't uncommon for that to work incorrectly and it wasn't a crash landing.

Interesting note for you: if the plane has an "older" ELT that still transmits on 121.5 that frequency isn't actively monitored anymore, and in Alaska they may be in a spot where there isn't a lot of traffic that actively monitors it. So ... it may go off, but be ineffective.

A working aircraft radio, on the ground, will not have the range it does in the air. In fact depending on where the antenna is mounted such as on the belly, it may not have much range at all.