Deep stall - Revision history

Bferrell at 14:59, 3 July 2012

2012-07-03T14:59:51Z

Bferrell at 14:59, 3 July 2012

2012-07-03T14:59:27Z

Bferrell at 14:57, 3 July 2012

2012-07-03T14:57:26Z

Bferrell at 14:52, 3 July 2012

2012-07-03T14:52:07Z

Bferrell at 14:51, 3 July 2012

2012-07-03T14:51:44Z

Bferrell at 14:51, 3 July 2012

2012-07-03T14:51:33Z

Bferrell at 14:48, 3 July 2012

2012-07-03T14:48:25Z

Bferrell at 14:48, 3 July 2012

2012-07-03T14:48:11Z

Bferrell at 14:47, 3 July 2012

2012-07-03T14:47:49Z

Bferrell at 14:45, 3 July 2012

2012-07-03T14:45:45Z

← Older revision		Revision as of 14:59, 3 July 2012
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	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>		After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>
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−


	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Velocity test pilot Carl Pascarell reported ([http://www.velocityxl.com/downloads.php?do=file&id=134 in that November 1991 kitplanes article]) riding the full stalled Velocity to the ocean in [[Lanza_N81VA\|N81VA]] without injury.<br/>		All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Velocity test pilot Carl Pascarell reported ([http://www.velocityxl.com/downloads.php?do=file&id=134 in that November 1991 kitplanes article]) riding the full stalled Velocity to the ocean in [[Lanza_N81VA\|N81VA]] without injury.<br/>

← Older revision		Revision as of 14:59, 3 July 2012
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−	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Velocity test pilot Carl Pascarell reported ([http://www.velocityxl.com/downloads.php?do=file&id=134in that November 1991 kitplanes article]) riding the full stalled Velocity to the ocean in N81VA without injury.

−	~~If we review~~ the ~~previous picture (above), we can see~~ that the ~~upper half~~ of the propeller ~~is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air~~. ~~The application of power may~~ cause the ~~lower half of~~ the ~~prop~~ to ~~produce more thrust than~~ the ~~upper half, which pushes the nose UP! Makes perfect sense once you think about it~~.<br/>	+	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Velocity test pilot Carl Pascarell reported ([http://www.velocityxl.com/downloads.php?do=file&id=134 in that November 1991 kitplanes article]) riding the full stalled Velocity to the ocean in [[Lanza_N81VA\|N81VA]] without injury.<br/>

← Older revision		Revision as of 14:57, 3 July 2012
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−	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991~~] - [http://www.velocityxl.com/downloads.php?do=file&id=133 Kitplanes December 1992~~]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>	+	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>


−	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? ~~Was this~~ the ~~result of~~ the ~~strake unstalling itself or is there another reason?~~ If we review the previous picture (above), we can see that the upper half of the propeller is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air. The application of power may cause the lower half of the prop to produce more thrust than the upper half, which pushes the nose UP! Makes perfect sense once you think about it.<br/>	+
		+	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Velocity test pilot Carl Pascarell reported ([http://www.velocityxl.com/downloads.php?do=file&id=134in that November 1991 kitplanes article]) riding the full stalled Velocity to the ocean in N81VA without injury.
		+
		+	If we review the previous picture (above), we can see that the upper half of the propeller is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air. The application of power may cause the lower half of the prop to produce more thrust than the upper half, which pushes the nose UP! Makes perfect sense once you think about it.<br/>

← Older revision		Revision as of 14:52, 3 July 2012
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	[[Image:deepstall.png\|450px\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG '''beyond the aft limit''', either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior. This is particularly worrisome when attempting a loop where airspeed decays rapidly in an unusual attitude where the weight might tend to make the aircraft slide backwards. Since there is no prop-wash on the rudders of a canard, it is not possible to use the rudder to recover from a hammerhead maneuver.<br/>		[[Image:deepstall.png\|450px\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG '''beyond the aft limit''', either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior. This is particularly worrisome when attempting a loop where airspeed decays rapidly in an unusual attitude where the weight might tend to make the aircraft slide backwards. Since there is no prop-wash on the rudders of a canard, it is not possible to use the rudder to recover from a hammerhead maneuver.<br/>
		+

	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=133 Kitplanes December 1992]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>		After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=133 Kitplanes December 1992]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>

← Older revision		Revision as of 14:51, 3 July 2012
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	Deep Stall is a aerodynamic stall condition that is difficult or impossible to correct and unstall the wing. In some flying tail aircraft it is the blanketing of the rear control surfaces by a stalled main wing. In a canard it is typically a stalled main wing, which the canard has no aerodynamic ability to nose down and correct.<br/>		Deep Stall is a aerodynamic stall condition that is difficult or impossible to correct and unstall the wing. In some flying tail aircraft it is the blanketing of the rear control surfaces by a stalled main wing. In a canard it is typically a stalled main wing, which the canard has no aerodynamic ability to nose down and correct.<br/>
		+

	[[Image:deepstall.png\|450px\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG '''beyond the aft limit''', either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior. This is particularly worrisome when attempting a loop where airspeed decays rapidly in an unusual attitude where the weight might tend to make the aircraft slide backwards. Since there is no prop-wash on the rudders of a canard, it is not possible to use the rudder to recover from a hammerhead maneuver.<br/>		[[Image:deepstall.png\|450px\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG '''beyond the aft limit''', either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior. This is particularly worrisome when attempting a loop where airspeed decays rapidly in an unusual attitude where the weight might tend to make the aircraft slide backwards. Since there is no prop-wash on the rudders of a canard, it is not possible to use the rudder to recover from a hammerhead maneuver.<br/>

← Older revision		Revision as of 14:48, 3 July 2012
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−	[[Image:deepstall.png\|~~300px~~\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG beyond the aft limit, either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior.<br/>	+	[[Image:deepstall.png\|450px\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG beyond the aft limit, either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior.<br/>

← Older revision		Revision as of 14:47, 3 July 2012
Line 1:		Line 1:
−	Deep Stall is a aerodynamic stall condition that is difficult or impossible to correct. In some flying tail aircraft it is the blanketing of the rear control surfaces by a stalled main wing. In a canard it is typically a stalled main wing, which the canard has no aerodynamic ability to nose down and correct.	+	Deep Stall is a aerodynamic stall condition that is difficult or impossible to correct. In some flying tail aircraft it is the blanketing of the rear control surfaces by a stalled main wing. In a canard it is typically a stalled main wing, which the canard has no aerodynamic ability to nose down and correct.<br/>


		+	[[Image:deepstall.png\|thumb\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG beyond the aft limit, either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior.<br/>

−	[[Image:deepstall.png\|thumb\|right\|Deep Stall]]The revised designs ensure that deep stalls occur only if the canard aircraft is built or operated beyond its approved limits. The most likely cause of a deep stall today is flying with the CG beyond the aft limit, either knowingly or unknowingly. Building errors that result in incorrect incidence angles on the canard or main wing can also be the cause. These issues should be identified and resolved during the aircraft’s test phase. Despite the rarity of deep stalls, some pilots express concern that unusual attitudes could alter the normally benign canard stall behavior.


		+	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=134 Kitplanes November 1991] - [http://www.velocityxl.com/downloads.php?do=file&id=133 Kitplanes December 1992]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.<br/>


−		+	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Was this the result of the strake unstalling itself or is there another reason? If we review the previous picture (above), we can see that the upper half of the propeller is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air. The application of power may cause the lower half of the prop to produce more thrust than the upper half, which pushes the nose UP! Makes perfect sense once you think about it.<br/>
−	After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls. The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG. This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151 Sport Aviation, July 1991] [http://www.velocityxl.com/downloads.php?do=file&id=150 Sport Aviation, September1991]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees. At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch. Strakes are known to be destabilizing and this demonstrates one reason why.
−
−
−
−	All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch. Some pilots reported that the propeller was “blocked” or “cavitating”. What would cause the nose to pitch up when adding power? Was this the result of the strake unstalling itself or is there another reason? If we review the previous picture (above), we can see that the upper half of the propeller is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air. The application of power may cause the lower half of the prop to produce more thrust than the upper half, which pushes the nose UP! Makes perfect sense once you think about it.

@@ Line 7: / Line 7: @@
 After deep stall testing was completed on the Velocity and Cozy IV, there was evidence that the strakes contributed to unrecoverable deep stalls.  The delta wing planform of the strake delays its stall and the strake’s center of lift is forward of the aircraft’s CG.  This was confirmed during low speed testing of the Velocity ([http://www.velocityxl.com/downloads.php?do=file&id=151
 Sport Aviation, July 1991]) which showed the wing and canard stalled at 18 and 20 degrees pitch angle while the strakes did not stall until 26 degrees.  At aft CGs, lift from the strakes were pulling the nose higher even after the canard had stalled; whereas canard stall normally results in a nose-down pitch.  Strakes are known to be destabilizing and this demonstrates one reason why.
 All the reports state that the application of power had almost no effect or resulted in a slight nose-up pitch.  Some pilots reported that the propeller was “blocked” or “cavitating”.  What would cause the nose to pitch up when adding power?  Was this the result of the strake unstalling itself or is there another reason?  If we review the previous picture (above), we can see that the upper half of the propeller is operating in turbulent flow from the stalled wing/strake, whereas the lower half of the prop is exposed to relatively clean incoming air.  The application of power may cause the lower half of the prop to produce more thrust than the upper half, which pushes the nose UP!  Makes perfect sense once you think about it.