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Author Topic: flying with an open window in a 172  (Read 5748 times)

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fredq

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flying with an open window in a 172
« on: November 04, 2009, 04:16:23 PM »
I had a passenger open the window on a Cessna 172 just as I was flairing for a landing.

It was a hot day in Moree Australia.

The increase in noise startled me and I made a 4 touchdown landing.  Can I log all 4??? 

My real question does opening the window change the way the 172 handles particularly on final with 20 degrees of flaps?

Fred
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ChinookDriver47

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Re: flying with an open window in a 172
« Reply #1 on: November 04, 2009, 04:42:07 PM »
My answer is no. Here's why:

Taking a look at the equation for the coefficient of lift, one can see that the biggest controlling factor we as pilots have over the overall lift on an airplane is what speed we opt to fly at ("s" squared). Since the surface area of a open window is not large enough to produce lift, and any drag would be negligible as opposed to any larger surface producing a known amount of parasite drag already accounted for when the aircraft is in a Vso configuration, other than the noise, you wouldn't notice any difference.

 However, if someone opened a door, then the change in performance would be immediately noticeable since you are changing the surface area of the aircraft exposed to the relative wind. You would have to make a much larger control surface and speed correction to account for your newly found parasite drag.

  Wow....college did teach me something.

 
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David B

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Re: flying with an open window in a 172
« Reply #2 on: November 04, 2009, 04:43:34 PM »
 Hi Fred.

Check the POH for operating limits.

In the 172s I fly the window can be open at any normal speed.  I fly all the time with the windows open and there is no difference with how the aircraft handles.  

I'm am going to remember to blame my bad landings on the windows in the future...

DavidB
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faintfuzzy

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Re: flying with an open window in a 172
« Reply #3 on: November 04, 2009, 04:46:24 PM »
You might notice a bit of float after chucking the offending passenger out the window with a direct relationship between the amount of float and the weight of your late passenger.

Rodg (Take no prisoners!) Petersen
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hotrod150

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Re: flying with an open window in a 172
« Reply #4 on: November 04, 2009, 06:04:53 PM »
.....In the 172s I fly the window can be open at any normal speed.  I fly all the time with the windows open and there is no difference with how the aircraft handles.  ....

  No offense, but I call BS on this one. During one of our rare heat waves a few months ago, I flew with the pilot's window open all the way up against the wing. There was a noticable yaw factor, & (strangely enough) it yawed away from the side with the open window, not toward it. Maybe with both windows open it would even out, but that's not the scenario in the original post. And landing is the phase of flight when I'd least want to experience uncommanded (and unwanted) changes in handling.

Eric
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Klaus

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Re: flying with an open window in a 172
« Reply #5 on: November 04, 2009, 06:18:18 PM »
   I used to fly a 172 with bad window latches. I finally got use to the sudden rush of air and noise, but the passengers would always light-up like the world was coming to an end.   :o :o

    Check your flight manual for the max speed the windows maybe opened... I install Bubble windows with a placard reading "129 Knots max. speed with window open".

Klaus Marx
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Don W.

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Re: flying with an open window in a 172
« Reply #6 on: November 04, 2009, 06:49:41 PM »
Not a 172 but I do it all the time in my 150. I flew with bad latches for quite a while too & got used to them coming open often. Have even opened both doors & used them to control the airplane. Works pretty good. If all the controls  except the trim fail I think I could get it down on the airport & walk away. Maybe even still have an airplane!
« Last Edit: November 04, 2009, 06:53:28 PM by Don W. »

tweetyloui

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Re: flying with an open window in a 172
« Reply #7 on: November 04, 2009, 07:47:44 PM »
Not a 172 but I do it all the time in my 150. I flew with bad latches for quite a while too & got used to them coming open often. Have even opened both doors & used them to control the airplane. Works pretty good. If all the controls  except the trim fail I think I could get it down on the airport & walk away. Maybe even still have an airplane!

Yes, it's a tad bit disconcerting to us non-pilots when those darn doors pop open min mid-flight. I've had this experience many times (pilot side) and have now become pretty desensitized!

Tweety 'likes her seat belt tight" loui  :)
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Pegasus

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Re: flying with an open window in a 172
« Reply #8 on: November 04, 2009, 08:47:59 PM »
I often fly a professional photographer around and every time he opens the window, the plane seems to balloon a little bit. Since I'm trying to hold altitude as exactly as possible, I see it every time. If I fly with the windows deliberately open, after the initial (very minor) change, I can't tell the difference in flying characteristics.

This is with the flaps up and at cruise airspeed. Never tried it while landing!

  - Ed
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Ddayle

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Re: flying with an open window in a 172
« Reply #9 on: November 04, 2009, 10:27:55 PM »
I flew a c150 that had a door that popped open for a while(been fixed). It allways happened on take off, & i never noticed a difference in handling.  I used to land,  but i learned to just wait  and  slow  & shut it after i get some altitude. I have never noticed any pitch or yaw changes,except while actually shutting it. It is only 1/2" out at that most. Its a buck fifty, how aero is it to begin with? DaveR
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stutzman

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Re: flying with an open window in a 172
« Reply #10 on: November 07, 2009, 07:09:28 AM »
However, if someone opened a door, then the change in performance would be immediately noticeable since you are changing the surface area of the aircraft exposed to the relative wind. You would have to make a much larger control surface and speed correction to account for your newly found parasite drag.

Well, its hard to argue with your theory, but years ago when I had a 172A, I took off from Petaluma, Ca and flew to North Bend.  It wasn't until I braked a little abruptly to make a taxiway turn off at North bend that I noticed that my door had been open for the entire flight.  Normal enough flight, but it sure annoyed me that the cabin heater wasn't working all that well!

Now I've never had the door open on me with Hula Girl.  Apparently its a very loud and startling event.  The plane is supposed to fly just fine though.  I ain't anxious to experience it.  A boring flight is a good flight.
Frank Stutzman
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stutzman

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Re: flying with an open window in a 172
« Reply #11 on: November 07, 2009, 07:12:18 AM »
    Check your flight manual for the max speed the windows maybe opened... I install Bubble windows with a placard reading "129 Knots max. speed with window open".

OK, its been a few years since I last flew a 172.  Can you actually get a 172 past 129 knots?
Frank Stutzman
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Ddayle

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Re: flying with an open window in a 172
« Reply #12 on: November 07, 2009, 07:30:13 AM »
 Stutzman; OK, its been a few years since I last flew a 172.  Can you actually get a 172 past 129 knots?
[/quote]    Power dive ;D
« Last Edit: November 07, 2009, 08:44:07 AM by Ddayle »
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David B

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Re: flying with an open window in a 172
« Reply #13 on: November 07, 2009, 08:00:49 AM »
.....In the 172s I fly the window can be open at any normal speed.  I fly all the time with the windows open and there is no difference with how the aircraft handles.  ....

  No offense, but I call BS on this one. During one of our rare heat waves a few months ago, I flew with the pilot's window open all the way up against the wing. There was a noticable yaw factor, & (strangely enough) it yawed away from the side with the open window, not toward it. Maybe with both windows open it would even out, but that's not the scenario in the original post. And landing is the phase of flight when I'd least want to experience uncommanded (and unwanted) changes in handling.

Eric

I'm sure that planes react differently depending on the model.  I fly a mid 70's 172 and 182.  Both have an arm on the window limiting the amount that it can be opened.  I always fly with the pilot's window open in the summer and notice no difference open or closed, or opening or closing the window.  When I rented a new 172 in Florida  I experienced the same thing.  It's been more then a decade since I've flown a 150 but I don't remember then being any different.  I'm not sure that I've ever flown a Cessna that the window could be fully opened against the wing though.

DB
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hotrod150

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Re: flying with an open window in a 172
« Reply #14 on: November 07, 2009, 09:50:43 AM »
  You have to disconnect whatever is holding the window in a partially-open position- this differs from model to model. I wouldn't want to fly my current 150D wit the window open straining against the hold-open- it's pretty puny. That's why I disconnect it & let the window fly all the way open for photo op's.

Eric
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