The International Cessna^® 170 Association

I agree with George on the vertical card compass. Thanks for getting me to hold off on the purchase of one for my 170B. I've been looking at all the vertical card compass units in every CRJ I fly, and don't like what I see. I am glad they are in a standby mode. The last plane I had really had a bad vertical unit. While turning back and forth 180 degree across course for ATC delaying vectors, I observed the vertical compass to freeze during the start of the turn and remain frozen throughout the turn and would only release and spin around to correct heading when the wings were leveled from the turn. Wouldn't want this type of perfomance in my 170B and am glad to be overhauling my wet compass.

I wonder how old those DC=9-10s are that Northwest is still flying? How many thousands of cycles and hundreds of thousands of hours? Still in 121 service. Makes my 54' 170B sound like it just came off the assembly line with 4500 hours. The only thing that worries me from time to time is what age is doing to the molecular structure of the various fittings of the airframe. I REALLY worry about those AN8 bolts on the lift struts. Wonder what it woud be like to descend after one of these bolts fails and one wing is standing straight up with the relative wind while the other is in normal position. Have only heard of this happening once before. I think I would have designed the struts to use two bolts at both wing and fuselage. Considering the safety of my family, would replacing these AN8 bolts on a five year schedule be reasonable? Seems most any other area of the airframe would need several parts to fail in order for ultimate failure...but only one of those AN8 bolts have to fail and it is all over. Thoughts and comments? I need to get in the recliner with a glass of red wine and make these thoughts go away

Gosh, John you did get me thinking! It would indeed ruin your your day to have one of the AN8 wing strut bolts fail. If it makes you feel better, there's nothing wrong with replacing them at regular intervals.

But after some more thought, I wouldn't worry too much. Strut-braced, high wing Cessnas have the lowest in-flight break-up rate of any light aircraft. In fact, the airframe failure rate is significantly better for the older 210s with struts than the fully cantilevered wing of the later models, if Aviation Consumer is to be believed. I would wager that in an overload condition, the horizontal stabilzer would fail before a wing strut bolt.

You and I are used to Transport Category airplanes, where fail-safe construction and systems are the norm. But the average light plane has many areas where the loss of a component or system would end the flight...the engine is the best example I can think of! But even airline jets can't eliminate all single point failures. The stripped stabilizer jack screw of the Alaska Airlines MD-88 is one example I can think of where the loss of a single component resulted in an fatal accident.

Aviation is risk management, as we all know. Wing and strut bolt replacement is worthwhile, if it increases your peace of mind. For me personally, the record speaks for itself...

By the way, what were the circumstances of the wing failure you refered to? I'm curious...See ya, Russ Farris

Just as an aside, the oldest DC-9-10 flying for Northwest, N930RC was built in 1965 First with Bonanza Airlines, then Air West, Southern and Republic; all merged into Northwest eventually. It's the oldest jetliner flying for a major US carrier. A 21 year old pilot hired in 1965 would be retiring about now! Russ Farris

It may be the oldest "jetliner" but it's not the oldest airliner by a long shot. There are Ford's, Fokkers, and Stinsons that are older than that and of course, there are DC-3's that are all over the world more than 20 years older than even the oldest 170.
RE: the wing lift strut bolts:
Changing those bolts might actually increase your risk unless the replacement bolts were magnafluxed and x-rayed. I'm surprised that they don't have unique inspection requirements and PN's due to their intended use.
Here's an example of similar risk I ran into once. I was asked to fly a friend in his Baron because his regular pilot was on vacation. The airplane had been painted 4 years previously and I'd not flown it since that time. While preflighting the airplane I came to the tail and lifted the elevators, one in each hand, to perform a symmetry check. To my surprise one lifted about an inch before the other even moved. (I later found out that the regular pilot never made this sort of check. He simply lifted one elevator, then wiggled the rudder, then checked the other elevator. He'd never checked them for symmetry or integrity between the two.) Now, the Beech Barons and Bonanza's are made the same back there. Inside the tailcone is a yoke that splits ending in two castings, each of which has a bearing through which passes an AN4-type bolt along with some washers and a castellated nut. That 1/4" bolt is the only thing that holds the elevator to the yoke which moves the elevators up and down. If it broke, the airplane would probably be lost!
I refused to fly it, and the shop intended to replace the bolt with another AN4 bolt because when the faulty loose one was removed it showed considerable deep scratches and signs of stress from being operated so long too loose. (Those guys were lucky they hadn't been killed a couple years ago!) But looking in the IPC it was evident that the bolt is actually assigned a special Part Number,...instead of simply specifying an AN4 bolt. When Beech (Raytheon) was contacted, they confirmed that the bolt might appear to be identical to an AN4 bolt, but that it was actually such a bolt that had been X-rayed and magnafluxed to eliminate the off-chance of a new bolt with a fracture, stress riser, or "bubble" or other flaw in it. They said that failure of that bolt was universally a fatal accident.
Now, I'm also curious about the event you heard of John, in which a lift-strut equipped Cessna failed in flight due to one of these bolts. One of the strong points of strut-braced Cessnas has always been that there has never been an inflight failure breakup of a strut-braced Cessna wing that was properly assembled. (There were two I've heard of, one of which involved a badly corroded lower attachment casting, located within the lower strut-end, which was known to have not been annually inspected for over 5 years, and the other due to an improper rebuild of a wrecked wing using incorrect parts.)
In any event, if I were ever to have the AN8 bolts removed from my struts, I'd have them magnafluxed at the least and X-rayed if possible. A greater concern, in my opinion, are the "blocks" held within the spar carry-through at the wing attach points above the headliner. Those are far more likely to be a problem than the lowly-stressed strut bolts.

I used to maintain an old DC-3 that used to be a United Airlines plane. The plane was bare aluminum but in the right light you could still see the outline of the logo. It had 55,000 hours on it but was in great shape. I sure enjoyed working on it. Ironicly one of the older gentelmen at our local CAP used to fly DC-3's for United but he couldn't remember if he had ever flown it. He had some good stories though.
Shawn

[quote="gahorn"]It may be the oldest "jetliner" but it's not the oldest airliner by a long shot. There are Ford's, Fokkers, and Stinsons that are older than that and of course, there are DC-3's that are all over the world more than 20 years older than even the oldest 170.

A DC-3 built in 1928? That would been something! Actually, since the DC-3 first flew December 17, 1935, it would be more accurate to say there are DC-3s more than 20 years older than the NEWEST 170! Russ Farris

P.S. Only a relative handful of the 803 pre-war commercial DC-3 built are still around. The vast majority (almost 11,000) were built from 1942 to 1946, as military models like the C-47 and C-53. Of the 15 or so I have flown, everyone of them was an ex-military airplane.

So the reality is, the vast majority are only three to 15 years older than our 170 fleet...

Oops. It was only a W-A-G I made as to the general time lapse between the two models. 17 vs 20 years of the oldest 170....IF you count 1935 as the first year. According to TWA, they made a record setting flight coast to coast in their first version of 13 hours 4 minutes during the night of Feb 18-19, 1933. (The aircraft design was actually begun in 1928.) They finished a promotional tour with the airplane and recommended some changes (increased hp and fuselage length) and those changes were incorporated into the final production aircraft (which subsequently was modified again) changing it from a DC-2 to a DC-3. (Compete Encyclopedia of World Aircraft, Gen, Ed.- David Donald)

Talking about old airliners made me curious about our fleet ot T-37s here at Sheppard. A little digging with the MX record folks revealed that we have one '56, two '57s and many more '58s and '59s. The rest of the fleet (about 90 or so) represent the rest of the production run through the late 60s. The highest time bird is a '58 model with 21,100.1 hours as of yesterday. As the Tweet is not pressurized, "cycles" on the fuse are not a concern. BUT...the real eye-opener is the number of landings...59,581
Consider that probably 30% or more of those were made by pre-solo LTs, its a wonder the wings don't resemble a sway-back mare! Yep, ol' Clyde and the boys built a pretty good airplane 50 years ago. But then, we already knew that, didn't we?

A strange high frequency vibration occurred periodically in a Cessna 206 I once owned. The entire airplane would vibrate and you could actually see the wing struts blur both fore and aft. Strangely, it would happen quite frequently, say two or three times per week, especially when descending through visible moisture, i.e, a cloud. Go figure ! Then it would not happen for maybe six months or so and then it would again occur for a while. Cessna said it was all my imagination and refused to take my reports seriously until one day I had a Cessna tech rep on board when the vibration occurred. It definitely got his attention and Cessna looked into the problem. Apparently it had also happened on at least one strut-winged 210- I read about it much later.
Can you guess the cause of this mystery ? It was the combination of wing attach bolts on that particular airplane. The holes, apparently were at the max size tolerance and the bolts at the minimum. Cessna suggested changing all the bolts, which I did and the vibration never occurred again !
Just something to think about when considering changing those bolts...
Rudy

Rudy, I'm surprised it took any argument to convince Cessna about any such thing in a 206. The Cessna 206 is famous for "singin' in the rain!" All 206's prior to 1986 did it. Those struts were a unique thing in the 206/210 series (common part number) and they all "sing in the rain."

George, that airplane wasn't just "singin' in the rain" it was more like a wet dog trying to shake itself dry in the rain- you could see the struts blurred ! And it happened most often flying in cloud or rain. Cessna never paid any mind to my many complaints until their tech rep experienced it. (Maybe because I was a dealer)
Changing all four strut bolts solved the problem...
I hate to think that this was a known problem !