SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jan 14, 2013, 04:42 PM
LiPo-Sucker & Airframe EMT
pugsam's Avatar
Charlottesville, Virginia, USA
Joined Aug 2010
3,606 Posts
Hmmmm....without getting tangled-up in semantics......I'm agreeing with you, Joel (it is a stall phenomenon), and simply suggesting that the MiG's T-tail adds to the difficulty of recovering.

WWU's problem starts when he pulls sharp up-elevator, As you say:

Quote:
Originally Posted by turboparker View Post
....Pulling the stick back abruptly on any plane will often cause an accelerated stall. If one wing stalls first (which is often the case), the usual result is an abrupt roll toward the stalled wing.....
At that point, the sharp-up elevator has put him in a high AOA, with the wings stalling (probably one before the other, as you say, causing an abrupt roll), and with the MiG's high T-tail surfaces (stab/elevator, rudder, or both) experiencing blanking as they are in the shadow of the wing.

Meaning the MiG is no longer in controlled flight. It is essentially a projectile, not responding normally to control.

Scooting along as a foamy missile, of irregular shape and very little mass, chaotic things are going to happen very quickly. Very likely, an unplanned one-point landing (unless he's at least a mistake or two high).

Bottom line: The MiG stalled and rolled, and recovery was more difficult due to its T-tail blanking.

I agree; no mystery there.

pugsam is online now Find More Posts by pugsam
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 14, 2013, 04:59 PM
Gopher huntin' stick jockey
turboparker's Avatar
East Bethel, MN USA
Joined Jul 2009
11,954 Posts
Tail blanking is only an issue during deep stalls. It does not happen during a transient accelerated stall - which is what you get when you pull the stick back abruptly at speed. The described behavior is classic high-speed stall - without any stab blanking effects. There was no loss of pitch-control, which means that the elevator was still working just fine. The roll was not caused by a loss of directional control. Planes with conventional tails also usually roll abruptly when put into an accelerated stall. It has nothing whatsoever to do with stab blanking.

Joel
turboparker is offline Find More Posts by turboparker
RCG Plus Member
Old Jan 14, 2013, 05:37 PM
The Luftwaffle
Waffleman's Avatar
United States, FL, DeLand
Joined Sep 2012
1,210 Posts
Mine has done it on two occasions. But never in a loop.
I like to make a low pass two feet away from my face, at low speed, then gunit and make a hard turn back down the field. If i try to turn before I gun it, It will suddenly roll and crash. The first time it caught me off guard, and I did crash. The second time, I was able to gun the throttle and apply oppisite aileron in time to save it.
Sometimes in a turn I realize the its about to stall and I apply a little bit of rudder to even it out.
It looks like its flying tail-heavy in the turn even when its not tail heavy at all.
Waffleman is online now Find More Posts by Waffleman
Reply With Quote
Old Jan 14, 2013, 06:07 PM
Gopher huntin' stick jockey
turboparker's Avatar
East Bethel, MN USA
Joined Jul 2009
11,954 Posts
Waffleman,

That sounds like a classic tip-stall to me.

Joel
turboparker is offline Find More Posts by turboparker
RCG Plus Member
Old Jan 14, 2013, 06:29 PM
The Luftwaffle
Waffleman's Avatar
United States, FL, DeLand
Joined Sep 2012
1,210 Posts
Most likely.
But dosen't what is being described here have some of the same elements as a tip stall?
Waffleman is online now Find More Posts by Waffleman
Reply With Quote
Old Jan 14, 2013, 06:40 PM
LiPo-Sucker & Airframe EMT
pugsam's Avatar
Charlottesville, Virginia, USA
Joined Aug 2010
3,606 Posts
Ok, I pulled-up the official NTSB accident report summary. This settles once - and for all - the petty bickering:

Aircraft Accident Report
Loss of Control While Maneuvering MiG-15, N502
Roanoke, Virginia
December 22, 2012

NTSB Number: AAR-13-05
NTIS Number: PB2013-910405
Adopted: January 11, 2013

Executive Summary
On December 22, 2012, about 1432 eastern standard time, an Eflite Mig-15, N502, was engaged in routine aerobatics over Roanoke, Virginia, when it crashed about 100 feet west of the central runway of its landing field (a parking lot). The pilot was not seriously injured, although the airplane was substantially damaged by impact forces. The airplane was owned by WWU Theatrical Flying ("WhiskeyTangoFoxtrot"), of Roanoke, Virginia, and was operating as an aerobatics demonstration and training aircraft under the provisions of 14 Code of Federal Regulations Part 91. The flight departed its landing field under visual flight rules. Visual meteorological conditions prevailed at the time of the accident.

Probable Cause

The National Transportation Safety Board determines that the probable cause of this accident was (1) the pilot's abruptly pulling the stick back, causing an accelerated stall which became a deep stall as the AOA increased to critical attitude; (2) one wing stalling first; (3) an abrupt roll toward the stalled wing; (4) loss of directional control; and (5) recovery being inhibited by T-tail blanking as a result of the aircraft's high T-tail surfaces being in the shadow of the deep-stalled wing.

Nanny-Nanny-Boo-Boo

In its submission for this accident investigation, WhiskeyTangoFoxtrot stated that it accepted "full responsibility" for the accident and, in response, implemented corrective actions to preclude such an accident from recurring. One of these actions was to integrate safety management system principles and practices into its flight test operations. Another was to practice, practice, practice.
pugsam is online now Find More Posts by pugsam
Reply With Quote
Old Jan 14, 2013, 07:49 PM
when down=up, up=expensive
whichwaysup's Avatar
United States, VA, Roanoke
Joined Apr 2012
2,760 Posts
Oh my word. You win pug. That was hillarious. Joel, you have to surrender this one. You may be right, but arguing with the NTSB will not bode well for your future flying operations!
whichwaysup is online now Find More Posts by whichwaysup
RCG Plus Member
Latest blog entry: Clever sayings
Reply With Quote
Old Jan 14, 2013, 08:03 PM
The Luftwaffle
Waffleman's Avatar
United States, FL, DeLand
Joined Sep 2012
1,210 Posts
What does WWU stand for???

And I got the "Whiskey - Tango - Foxtrot" thing...
Waffleman is online now Find More Posts by Waffleman
Reply With Quote
Old Jan 14, 2013, 08:22 PM
Parkzone junkie
kalmon's Avatar
United States, MI, Grand Traverse
Joined Oct 2008
3,659 Posts
Quote:
Originally Posted by Waffleman View Post
What does WWU stand for???

And I got the "Whiskey - Tango - Foxtrot" thing...
WWU = WhichWaysUp

---
WWU, one thing we never considered: Make sure that each elevator half moves the same amount while under load. I've seen the pushrod tubes come lose an while under load they bow out and cause that side of the elevator to move less than the other half. Hard to find as when there is no load and the plane is just sitting they move the same amount as the tube doesn't push out!

Just something to look at.

-Brian
kalmon is offline Find More Posts by kalmon
Reply With Quote
Old Jan 14, 2013, 08:53 PM
Registered User
United States, TN, Jackson
Joined Mar 2007
4,019 Posts
Hmmm---Have any of you considered that this is a MODEL that is subject to us modelers creating other than realistic CG conditions as per the full scale plane???...And that this MODEL has a flat bottom airfoil that is NOT conducive to inverted flight???...Add in massive amounts of down elevator to just keep the model level in inverted flight just aggravates the problem with outside manuevers...

2+2=4...Simple as pie---Whatever analogy you want to use---C'mon guys---Use some common sense instead of over analyzing the obvious!!!........

Kevin

PS---Plus MANY points for making a seemingly complex subject easy for anyone to understand......
Kevin Greene is offline Find More Posts by Kevin Greene
Reply With Quote
Old Jan 15, 2013, 04:09 AM
BMFA 190658
SilentPilot's Avatar
United Kingdom, Yeadon
Joined Mar 2007
4,514 Posts
Quote:
Originally Posted by turboparker View Post
Tail blanking is only an issue during deep stalls. It does not happen during a transient accelerated stall - which is what you get when you pull the stick back abruptly at speed.
I don't get this

I thought that a Stall occurs when a wing is asked to go beyond its critical AoA. Going beyond the critical AoA with a high tailplane risks shadowing the elevator...

As a side note,
If (like I assume they do) tailplanes create negative lift to balance the aircraft then why do aircraft designers not place them in such a way that as soon as a wing is set to stall the stab goes into the wing shadow, causing it to lose effectiveness and unstall the wing?



Tony
SilentPilot is online now Find More Posts by SilentPilot
RCG Plus Member
Latest blog entry: Parkzone Ka8 telemetry install
Reply With Quote
Old Jan 15, 2013, 07:03 AM
Parkzone junkie
kalmon's Avatar
United States, MI, Grand Traverse
Joined Oct 2008
3,659 Posts
Quote:
Originally Posted by SilentPilot View Post
If (like I assume they do) tailplanes create negative lift to balance the aircraft then why do aircraft designers not place them in such a way that as soon as a wing is set to stall the stab goes into the wing shadow, causing it to lose effectiveness and unstall the wing?

Tony
Basically, you use the CG to pull the nose back down and un-stall the wing. so as the wing stalls it produces less lift, meaning the force of gravity acting on the CG ahead of the Center of Lift will cause the nose to lower and then in turn the angle of attack of the wing to lower, which lets the wing start flying again.

The reason for doing this and not as you described is you'd never want to cause the loss of flow over the control surfaces. If for some reason the CG was incorrect (aft) and the elevator was blanked by the wing there would be no way to bring the nose down, thus the plane would fall, in a stall, all the way to the ground.

(the above is a very simplified synopsis of the topic)
-Brian
kalmon is offline Find More Posts by kalmon
Reply With Quote
Old Jan 15, 2013, 07:38 AM
Registered User
Valkpilot's Avatar
Joined Mar 2012
703 Posts
Quote:
Originally Posted by pugsam View Post
How's the rest of it?

If everything else is in good shape -- especially the control surfaces -- just repair the nose as best you can and keep flying! (You may have to ignore occasional snarky comments, from low-lifes who probably also kick dogs.)

It worked! Took off the canopy, brought a pot to boil, turned it off, 2 min dunk,
and it's back to normal, albiet slightly weathered looking. And as for "public
opinion" , since I usually fly Monday mornings, I'm usually alone, unless my brother decides to join me with his planes, none of which he's had a sucessful flight with.
Valkpilot is offline Find More Posts by Valkpilot
Reply With Quote
Old Jan 15, 2013, 08:01 AM
BMFA 190658
SilentPilot's Avatar
United Kingdom, Yeadon
Joined Mar 2007
4,514 Posts
Thanks Brian
SilentPilot is online now Find More Posts by SilentPilot
RCG Plus Member
Latest blog entry: Parkzone Ka8 telemetry install
Reply With Quote
Old Jan 15, 2013, 09:22 AM
Gopher huntin' stick jockey
turboparker's Avatar
East Bethel, MN USA
Joined Jul 2009
11,954 Posts
The NTSB report cited one wing stalling first as the reason for the sudden roll - not stab blanking. (Same thing I said about the model.) I still stand by my original statement that stab blanking is not involved when abruptly pulling the stick back on a UMX MiG 15 & putting it into an accelerated stall. It's simply a textbook case of high-speed stalling. Nothing more.

Joel
turboparker is offline Find More Posts by turboparker
RCG Plus Member
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Official Eflite UMX Beast Owners thread! darksiede Micro Ready-to-Fly 18429 Oct 14, 2014 02:13 PM
Discussion E-flite UMX MiG 15 DF SNEAK PEEK! D PAYNE Micro EDF Jets and Power Systems 2222 Oct 10, 2014 05:15 AM
Discussion Hobbyking Lancaster official owners thread Tartago Electric Warbirds 979 Aug 10, 2014 11:58 AM
Discussion UMX Mig-15 DF Mod Thread NitroCharged Micro EDF Jets and Power Systems 1132 Aug 01, 2014 04:30 PM
Sold Eflite F-86 Sabre 15 DF NIB! blue7.62 Aircraft - Electric - Jets (FS/W) 1 Apr 05, 2012 01:35 PM