The International Cessna 170 Association

I have forever been meticulous in securing the cowl doors on my C170B. SN 26433.

I understand that cowl locks are a concern with only the C 170A

All of which leads me to the question. Is the cowling door pooping open in flight a big deal in any model C 170?

Has an open cowl door ever figured in a reportable incident in any model C170?


Regards

I did a quick search of NTSB records limited to Cessna 170B and found one in recent years involved a cowl unlatching in flight (See NTSB# ANC09LA088) 8/25/2009 reportedly in Anchorage AK. Witnesses reported that shortly after takeoff, the right engine access cowling opened and the airplane began a step left turn back to the airport. As the left bank increased, it descended nose first into tundra covered terrain. Pilot was only occupant and suffered serious injury. NTSB Probable Cause: The pilot's decision to make an abrupt and steep low altitude turn just after takeoff, while attempting to return to his departure airport resulting in an aerodynamic stall and loss of aircraft control. Contributing to the accident, was the pilot's failure to ensure the airplane's engine access cowl was latched before takeoff.

This finding suggests that the cowl opening did not adversely affect flight characteristics and the pilot should have continued climb to a safer altitude before turning back to land. There have probably been other cases where the cowl opened in flight with no accident or incident. The cowl in those cases probably had damage. I remember a post on this forum from a 170A owner trying to find a replacement cowl after an inflight opening. It might be interesting to search ASRS (NASA) reports to see if there is any info. ASRS, a non punitive voluntary reporting system can yield valuable information on specific aircraft types. In looking at the 170B accidents, it is clear that over 90% involve loss of control on takeoff or landing with variable wind conditions frequently cited by NTSB. Cowling incidents appear very rare.

I think some light twins have had baggage compt door pop open with crashes as well. Fly the plane Dudes!!

A friend of mine had the door on the R/H side of his late B model open up in flight. He fabricated a new one using like material from the one previously installed. Guess what happened on his test flight? So, he contacted some other people in the know and found that the original drawings indicated a thicker material than what had been on his plane. Sorry, do not recall the thickness it was supposed to be, but the thinner (I think he initially used .032" aluminum) material couldn't hold back the pressure at higher airspeeds (a la descending out of cruise altitude) and would pop open. Just something to think about...

Cowls coming open in flight has occured on all the 170 models. It is not uncommon due to forgetfullnes or worn parts. In the 170 Association publication "Service Related Articles Manual - Cessna 170 Series", member Tom Schulke talks about when his 170A cowl came open and how he fixed the problem. My 170B left cowl door came open at altitude, and made a horrible racket. At least it did not come off and damage the tail, so I flew the plane another 40 miles to a nearby airport to make temporary repairs . If you search the forum you should find pictures of how I solved the problem by converting to a single 172 cowl inspection door. (I don't know how to attach the forum link here) In another 170 Association publication "The Cessna 170 - Thirty-Six Years Of A Classic" 1984 edition, member Benjamin Tilton also shows how to solve the problem on the "A" model. Email Jan Billeb, the Executive Secretary, she may have copies of a more resent publication update. If you attend any of the local 170 flyins, or 170 Annual Convention, you can also see first hand how others have "fixed" their cowls. I may stand corrected, but I believe the founding fathers of the 170 Association (John D. Benham and Bill Wehner) started the association because of lack of Cessna support on cowl latches.

I've seen later cowl doors open in flight with expected bending of that door. However the '52 and earlier cowl latches are, in my opinion, not reliable enough to be considered airworthy without some addition locking mechanism. They were probably suspect when the parts are where new, now that they are worn, they just can not be trusted to stay in the locked position by themselves.

And when one side opens on the '52 and earlier cowl it will really destroy the cowl and maybe cause other damage. And it has not been unheard of for a pilot with a '52 and earlier cowl that has opened to wreck their plane trying to get it on the ground in an expeditious manner. This is exactly what happened to my 170. The cowl came open and it was ground looped on landing ripping the gear box out of the fuselage for the second time in less than a year. Reported accident? Hell no not in those days.

For those who have not had this...experience...here's what it looks like. Mantra repeated to myself throughout the approach to landing: "Fly the airplane" (so as not to end up further damaged as Bruce suggested above)
Note BOTH latches are screwed in.

It's the upper part of the latch that needs to be secured . This is usually accomplished with a drilled bolt through the backside of the upper cowl through a hole drilled in the latch and secured with a small hitch pin. This of course keeps the upper cowling from coming loose from the latch and scaring you. Keep a roll of packing tape in the plane just in case none of this works....

Josh that is a bad day.

There are two failures of this latch. The first and I feel less prevalent, but I could be wrong is what happened to Josh. The upper latch slipped off the cowl catch. Probably the front then the back was ripped out.

This photo shows that the top of the latch is not flat and captures the cowl catch. If either is worn it will let go. I've seen some of the catches with a dimple punched at the top edge to insure it catches the cowl catch. not sure if the dimple is a mod to original by owners or original. A small rivet squeezed in the same place might work as well as a dimple. As Ed suggested securing the top to the latch to the cowl or pinning it on is an answer. I feel it is more prevalent though that the bottom of the latch does not stay locked down and releases. The screws in Josh's picture where to fix that. When new the parts relied on a spring clip engaging the inside of the latch and holding it. Most by now are warn or the clip broke and that will not work.

I also think the front two latches are more critical. If they go the whole cowl door will be pulled open. I've had just the rear latches pop and besides scaring me into thinking what might happen next, there was no harm done.

shows to go ya, its more of a condition of parts than a lack of a safety.

That will ruin your day. I'm sure that startled the hell out of you when it happened, didn't it Josh?

Makes the Dip Davis latch STC look pretty good...

Ryan Smith wrote:.....Makes the Dip Davis latch STC look pretty good...

But the Davis are so dam ugly in my opinion. The style of the 170 begs for a latch exactly like it has not the more modern clean looking Davis solution which looks like it should be on a sweep back tail 172 with a nose gear.

I hold just the opposite opinion and think they look beautiful! (just paint them and they'll be invisible)



Dzus style

or wing style


And only $250 (but I can't imagine why one cannot simply do it as a minor alteration.)

Bruce Fenstermacher wrote:

Ryan Smith wrote:.....Makes the Dip Davis latch STC look pretty good...

But the Davis are so dam ugly in my opinion. The style of the 170 begs for a latch exactly like it has not the more modern clean looking Davis solution which looks like it should be on a sweep back tail 172 with a nose gear.

Actually, the first time I saw the Dip Davis latch, I shared Bruce's opinion. But, the bent-up cowling and expense of replacing that cowl are waaayyyy uglier than the latches. I think 43A will be sporting a set of them soon...

And yes, Ryan, did startle me a bit! Thankfully I didn't have to break out the leather cleaner!

For what it's worth I had a cowl door pop open in flight and the results looked much like what KS170A has pictured. There's nothing you can do in the air except slow the plane down and put it in a slight skid, just enough to keep the flapping mess flopped over to one side while you limp it to a landing.

I ended up rolling out my own new doors and I believe I used .030 sheet. The original doors were about 020, but they had a doubler around the edge that had been spot welded on and helped hold the curve. I also decided on going with the DipDavis mod, and it's been working fine for the last 200 or so hours. My one complaint is that the DipDavis latches don't apply a constant tension on the doors as the springs in the OEM latches did.
Chris