Author Topic: A purely hypothetical question (for now...)  (Read 6984 times)

Offline Zaffex

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A purely hypothetical question (for now...)
« on: July 19, 2007, 02:27:44 PM »
Is it possible to fly a conventional aircraft backwards in straight-and-level flight? Or is it just plain impossible? I was thinking along the lines of a turboprop like the Turbo Raven, with really good reverse thrust.
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Offline AirScorp

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Re: A purely hypothetical question (for now...)
« Reply #1 on: July 19, 2007, 05:20:42 PM »
In short, no, I think it's crazy  ::rofl::..
Multiple times the drag, minimal lift and controls that would then be leading-edge and possibly reversed..

But you can actually fly backwards in a UL if the headwind is high enough (positive airspeed, negative ground speed)  ::knockedout::
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Offline Zaffex

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Re: A purely hypothetical question (for now...)
« Reply #2 on: July 19, 2007, 11:34:06 PM »
Well, yeah, I guess I should've specified reverse as in reverse flow through the air.
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Offline Gulfstream Driver

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Re: A purely hypothetical question (for now...)
« Reply #3 on: July 20, 2007, 06:43:19 PM »
A buddy of mine did it in an acro bird (forget the type) for a second.  Kind of freaked him out because the controls reversed.
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Offline Baradium

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Re: A purely hypothetical question (for now...)
« Reply #4 on: July 22, 2007, 07:41:04 AM »
A buddy of mine did it in an acro bird (forget the type) for a second.  Kind of freaked him out because the controls reversed.

Sounds like you're talking about a tail slide...   the thing is that it couldn't have sustained flight that way.


The only aircraft I can think of that might have been able to do it would've been the wright flier, becuase it had non direction airfoils and a nuetral balance.... both of which probobly would have killed you if you'd tried to change between aspects of flight.  Also due to it's design, it couldn't have actually taken off going backwards anyway.


With a conventional aircraft and standard airfoils, you'll have trouble trying to produce lift.  Any type of angle of attack will produce a stall due to the knife edge of the trailing edge of the wing.  That's ignoring aspects such as the weight and balance etc.   CG on a conventional aircraft is forward of the wing, flying backwards it'd be aft.... thus the aircraft would want to pitch up and stall.  So even if you could get the airfoils to produce lift, you'd have an extremely unstable aircraft.   
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Offline undatc

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Re: A purely hypothetical question (for now...)
« Reply #5 on: July 25, 2007, 05:15:58 PM »

But you can actually fly backwards in a UL if the headwind is high enough (positive airspeed, negative ground speed)  ::knockedout::


Did this all the time here at UND when I was getting my license.  Find a nice 50 or 60 knot head wind, take her into slow flight and watch the GPS give us -5 on ground speed.  So much fun.  Gave my instructor grief one day, asking him if he was teaching me to fly helicopters or airplanes?
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airtac

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Re: A purely hypothetical question (for now...)
« Reply #6 on: July 26, 2007, 07:17:48 AM »

But you can actually fly backwards in a UL if the headwind is high enough (positive airspeed, negative ground speed)  ::knockedout::


Did this all the time here at UND when I was getting my license.  Find a nice 50 or 60 knot head wind, take her into slow flight and watch the GPS give us -5 on ground speed.  So much fun.  Gave my instructor grief one day, asking him if he was teaching me to fly helicopters or airplanes?

Gee, North Dakota must be a really tough place to learn to fly with those 50 or 60 knot winds all the time-----------------Is that story really true?-------NO----------That's not even poetic license, that story is simply not true!!!!
WE GROUND FIRE AIRCRAFT (fixed wing, flown by high time professionals) IF THE SURFACE WINDS EXCEED 35 KNOTS OR WINDS AT 3,000 EXCEED 50 KNOTS---just how high do these UND trainers fly?
« Last Edit: July 26, 2007, 08:00:32 AM by airtac »

Offline Gulfstream Driver

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Re: A purely hypothetical question (for now...)
« Reply #7 on: July 26, 2007, 06:01:57 PM »
Whoa, Jim.  You feeling ok?  Stressed out or anything? 

It didn't happen that often with my flight training, but I think we did go backwards a couple of times.  I had a high wind endorsement for 29 knots while I was there.  A buddy of mine was able to get a Katana into ground effect using less than 10 ft of runway.  It does get windy.  And the instrutors like to get pretty high to work on maneuvers.  It's like they don't trust their students or something.
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Offline undatc

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Re: A purely hypothetical question (for now...)
« Reply #8 on: July 26, 2007, 06:13:26 PM »

Gee, North Dakota must be a really tough place to learn to fly with those 50 or 60 knot winds all the time-----------------Is that story really true?-------NO----------That's not even poetic license, that story is simply not true!!!!
WE GROUND FIRE AIRCRAFT (fixed wing, flown by high time professionals) IF THE SURFACE WINDS EXCEED 35 KNOTS OR WINDS AT 3,000 EXCEED 50 KNOTS---just how high do these UND trainers fly?

Before you jump all over my ass like you so love to do, you just check your facts.  We fly all the time with surface winds of 20 to 30 knots.  Our cut off is 30 knots at the surface.  If we didn't fly with that amount wind, we would never get off the ground.

Now meteorology 101 should come into play here, but oh yea I forgot, you never open books, all of your knowledge comes for years of experience.

Met 101 tells us that wind is slowest at the ground due to skin friction drag, and this skin friction drag comes into effect in the boundary layer of the atmosphere (the first 2,000' agl).  Also we all should know that wind increases with altitude, and you see the greatest increase in wind speed in the fist few thousand feet after that boundary layer. 

So you then apply this knowledge to practical use, you take off with a ground wind speed of 30 knots, which I've done here.  You climb up to cruising altitude for me that day was 5,500' on the way to fargo.  I had a tail wind going down, and was with a TAS of 115 my ground speed was reading 175.  Now I assume you can do simple math that gives me a relative wind of 60 knots roughly.  I made it to fargo in about 15 min, normally about a 30 min trek in a warrior.  On the way home, several hours later, as my instructor and I figured we'd never make it back with that kinda head wind, our TAS was 105, with a GS of 70ish.  We watched cars pass us on the interstate all the way back to Grand Forks.

If you think I'm using poetic license or swamp gas smoke and mirrors to tell my story here, ask Gulfstream.  He went to UND and still lives in this area.  He will readily confirm what I say here.

**Edit, Gulf beat me to it.
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Offline Baradium

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Re: A purely hypothetical question (for now...)
« Reply #9 on: July 26, 2007, 10:15:40 PM »
I do have a question... what kind of GPS showed a -5?  Seems it would have just decided you had switched directions and were going 5 kts in the other direction....

Of course, we've got pretty old school GPS units, you might have much smarter ones.


I had a day once where I was pretty confident I could have gotten the 1900 to a near zero or possibly negative ground speed.   Don't think the pax would have appreciated the humor as much as us though...

With the fire aircraft, do you ground aircraft in stages or all of them?    IE, conventinoal gear / slower aircraft then the big guys? 


Chris, what are the cutoffs for gusts?  Cross wind?   


30 kts is a whole lot of wind if you get into an area on the airport that is shielded and the winds dies away, losing 20 or so kts can be fun in the 1900, must be even more so in something a lot slower and with the lower power output of the warrior.
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Offline undatc

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Re: A purely hypothetical question (for now...)
« Reply #10 on: July 27, 2007, 01:51:30 AM »
I do have a question... what kind of GPS showed a -5?  Seems it would have just decided you had switched directions and were going 5 kts in the other direction....

Of course, we've got pretty old school GPS units, you might have much smarter ones.


I had a day once where I was pretty confident I could have gotten the 1900 to a near zero or possibly negative ground speed.   Don't think the pax would have appreciated the humor as much as us though...

With the fire aircraft, do you ground aircraft in stages or all of them?    IE, conventinoal gear / slower aircraft then the big guys? 


Chris, what are the cutoffs for gusts?  Cross wind?   


30 kts is a whole lot of wind if you get into an area on the airport that is shielded and the winds dies away, losing 20 or so kts can be fun in the 1900, must be even more so in something a lot slower and with the lower power output of the warrior.

It did show -5.  Reason being, is that the Garmin GPS's we use you can put in your route of flight, the "magic pink line" as the CFI's like to call it.  And as long as you're moving forward on it, it shows positive speed, but if you go backward on your route it shows negative.  I suppose you could turn that function off, but I dont know how.  All I know about the GPS is a big Garmin unit with lots of buttons and a huge screen.

The 30 knots is a total wind component, not sure what the cross/head wind are each, id have to look them up in our flight policies, they may have changed even (the info I'm going off of was from Spring of '06).  And as far as I know that 30 knots is for every one, but I'm not sure on that as I wasn't really concerned with our Arrows or Seminole's at the time, I can try to find out for you, several friends here are CFI's.

And 30 knots here, when it does get there is pretty much sustained, the wind here in unrelenting.  I've only ever flown twice with that much wind, the X-country to Fargo, and one other local flight.  Only reason I went on those days is cause the wind was right down the runway, no cross wind at all basically.
-the content of the previous post does not represent the opinions of the FAA or NATCA, and is my own personal opinion...

airtac

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Re: A purely hypothetical question (for now...)
« Reply #11 on: July 28, 2007, 04:01:12 AM »


Now meteorology 101 should come into play here, but oh yea I forgot, you never open books, all of your knowledge comes for years of experience.

"you never open books"---I think that's an incorrect assumption on your part, I was merely pointing to to the "did this all the time" statement in your original post.  I just feel your unbounded enthusiasm sometimes makes you paint with a wide brush---no need to be obstreperous in your reply.
And I am sorry if my 49 years of experience offends you----How about we go back to having fun, accurately.  :D

Offline TheSoccerMom

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Re: A purely hypothetical question (for now...)
« Reply #12 on: July 30, 2007, 01:58:15 AM »
And I am sorry if my 49 years of experience offends you----How about we go back to having fun, accurately.  :D

Uhh....  umm...  so, uh, I got a question.   

Did you really get a new Peterbilt after just 49 years?!?   Sheesh!  Don't you have any kind of warranty on that baby?!?


 ::rofl::         >:D              :o
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airtac

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Re: A purely hypothetical question (for now...)
« Reply #13 on: August 04, 2007, 05:53:29 AM »
And I am sorry if my 49 years of experience offends you----How about we go back to having fun, accurately.  :D

Uhh....  umm...  so, uh, I got a question.   

Did you really get a new Peterbilt after just 49 years?!?   Sheesh!  Don't you have any kind of warranty on that baby?!?


 ::rofl::         >:D              :o
OH MOM!.

Offline Rooster Cruiser

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Re: A purely hypothetical question (for now...)
« Reply #14 on: August 05, 2007, 12:39:03 AM »
Part of the joys of flying in the upper midwest is learning how to deal with high winds.  When I lived in South Dakota, we used to say that our windsock was a log chain wrapped around a flagpole.  If the log chain wasn't sticking straight out, it was a good day to fly.  In reality I would take students up at surface winds of up to 30 kts to build their confidence.  Several times I had students practicing slow flight into the wind, and we would note that our C152 was actually going backwards versus the ground (no GPS).
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