HP limits on M20 Airframe??

[Capt_CrashN_Burn]

Is there a reason that the 350hp version of the TSIO-550 has never been used in the Acclaim type S??

Mooney could then brag about building a plane that does 260+ KTS.

The highest HP Mooney that I've heard of is the 351 Rocket conversion that has 335 HP, I hear they do about 250 kts, but they suffer from the extra weight of a liquid cooling system.

Anyone have any guesses??

[Kwixdraw]

There are all sorts of possible reasons not to do that engine mod. It could be related to flutter speeds or just not having tested for flutter at those speeds. Any number of engineering concerns would make it a no go.

[Capt_CrashN_Burn]

Quote: Kwixdraw

There are all sorts of possible reasons not to do that engine mod. It could be related to flutter speeds or just not having tested for flutter at those speeds. Any number of engineering concerns would make it a no go.

[tony]

Then they would be flying at speeds that are well outside the published flight envelop and would be considered a test pilot, not a private pilot.

[rbharvey]

High Altitude Cruise in the Acclaim is around 160-165 KIAS, with Vne placard at 194, so I m betting you could get another 15 kts and that is right up against the airframe limits. So maybe 255kts def not going to get into the 260s

[Kwixdraw]

You don't want to be pushing it that hard anyway. Go to the Van's aircraft website. Van has an article in there about why you shouldn't cram the biggest prop twirling device in the airframe that can possibly be shoved in there. I think it's Martin Hollman at Aircraft Design Inc. that sells books and computer programming for those who must experiment. You should see his cgi demos of flutter modes. Long and short is that you don't want to be pushing redline at high altitude and hit some unexpected turbulence....it's a long fall from up there when the wings come off or the tail departs.

[DaV8or]

At some point, if you really want to go faster, you should be looking at something with a turbine on it and and airframe designed for those faster speeds. When you figure than what Al designed was made of wood and only was supposed to have 160hp on the nose, people already have pushed the design, probably to it's limits now. On the other hand, I suppose if you really wanted to make a Mooney that had amazing climb performance, you could hang even greater HP out front and then put on a more climb specific prop. That might be a case for more HP.

[Rocket_Driver]

Quote: Capt_CrashN_Burn

Is there a reason that the 350hp version of the TSIO-550 has never been used in the Acclaim type S??

Mooney could then brag about building a plane that does 260+ KTS.

The highest HP Mooney that I've heard of is the 351 Rocket conversion that has 335 HP, I hear they do about 250 kts, but they suffer from the extra weight of a liquid cooling system.

Anyone have any guesses??

[jetdriven]

Flutter is based on TAS not IAS, and someone in a RV found out the hard way just as you said.  He hit a nice bump and that excited the airframe into flutter.   it was all over from there.

http://www.vansairforce.com/community/showthread.php?t=72316

thats the wrong article

www.vansaircraft.com/pdf/hp_limts.pdf

Quote: Kwixdraw

You don't want to be pushing it that hard anyway. Go to the Van's aircraft website. Van has an article in there about why you shouldn't cram the biggest prop twirling device in the airframe that can possibly be shoved in there. I think it's Martin Hollman at Aircraft Design Inc. that sells books and computer programming for those who must experiment. You should see his cgi demos of flutter modes. Long and short is that you don't want to be pushing redline at high altitude and hit some unexpected turbulence....it's a long fall from up there when the wings come off or the tail departs.

[ChrisH]

Date:	05-MAY-1998
Time:	0930
Type:	Mooney M20K
Operator:	private
Registration:	N231BY
C/n / msn:	25-0115
Fatalities:	Fatalities: 1 / Occupants: 1
Other fatalities:	0
Airplane damage:	Written off (damaged beyond repair)
Location:	Bakersfield, CA -    United States of America
Phase:	En route
Nature:	Executive
Departure airport:	Sacramento, CA (SAC)
Destination airport:	, CA (L45)

Narrative:
While descending for an instrument approach in instrument meteorological conditions, the airplane's airspeed exceeded its never exceed velocity (Vne) of 196 knots. The elevators fluttered and separated from the airplane. Thereafter, the stabilizers departed, the nose pitched downward, and both wings failed in a negative direction. A ground witness heard a 'pop' sound, and observed airplane parts falling from the low clouds; the surface winds were reported by the witness as gusty. Earlier during the flight, the pilot had been cruising about 19,000 feet, and tracking in a southerly direction at 191 knots (ground speed). The winds aloft were westerly. While communicating with flight watch and radar controllers, he indicated that his airplane was not equipped with deicing equipment. The pilot was advised that icing conditions existed between 13,000 and 15,000 feet, and the freezing level was 7,000 feet. Due to traffic, at 0923 the controller cleared the pilot to descend to 15,000 feet. The pilot accepted the clearance, and requested a clearance to divert to a nearby airport. The controller approved the request. During the last 24 seconds of radar-recorded flight, the airplane's rate of descent increased to 3,500 feet per minute, and over its southerly course its ground speed increased to 240 knots. Shortly after this at 0930:21, the sound of an emergency locator beacon was recorded in the radar control facility. Pilot reports covering the area of the accident around the time of the event reported light to moderate turbulence and light to moderate rime/clear icing conditions. Engineering analysis and testing by the airframe manufacturer predicted the onset of flutter to occur at 241 knots. The airplane was modified by the installation of a larger engine with 95 additional horsepower available. CAUSE: The pilot's operation of the airplane at a speed well in excess of it's designed never exceed speed that resulted in elevator flutter and in-flight failure of the airplane. Turbulence and icing conditions were factors in the accident.

[Shadrach]

Quote: jetdriven

 

[Shadrach]

Bump...

I'd like to get some feedback on the above post... If VNE is based on TAS and Mooney is selling the Acclaim as a ~240kt airplane with a VNE of 194kts, how are they meeting ceritifcation standards. Are Acclaim pilots legally flying around at altitude with negative flutter margins???  I doubt this to be the case, so I'm trying to reconcile it in my head. Perhaps I need more coffee?

[201er]

VNE is published in the limitations in KIAS. Flutter is based on a certain true airspeed. They probably figured that if you don't exceed the indicated VNE speed below the service ceiling, you won't reach the flutter speed.

[Shadrach]

Quote: 201er

VNE is published in the limitations in KIAS. Flutter is based on a certain true airspeed. They probably figured that if you don't exceed the indicated VNE speed below the service ceiling, you won't reach the flutter speed.

[Ron McBride]

Remember Ground Speed and TAS are completley different.  You can have a TAS of 150 Knots and add a 100 Knot tailwind for a ground speed of 250 Knots.

Engineering analysis and testing by the airframe manufacturer predicted the onset of flutter to occur at 241 knots.

Flutter is based on a certain true airspeed.

Ron

[jetdriven]

I think flutter margins can be increased with increasing the mass balance of the control surfaces.  There is a limit to everything, however. I bet the Acclaim is getting pretty close.

[Shadrach]

Quote: N9154V

Remember Ground Speed and TAS are completley different.  You can have a TAS of 150 Knots and add a 100 Knot tailwind for a ground speed of 250 Knots.

Engineering analysis and testing by the airframe manufacturer predicted the onset of flutter to occur at 241 knots.

Flutter is based on a certain true airspeed.

Ron

[aviatoreb]

Quote: jetdriven

I think flutter margins can be increased with increasing the mass balance of the control surfaces.  There is a limit to everything, however. I bet the Acclaim is getting pretty close.

[KSMooniac]

Quote: jetdriven

I think flutter margins can be increased with increasing the mass balance of the control surfaces.  There is a limit to everything, however. I bet the Acclaim is getting pretty close.

[Shadrach]

Scott,

The way I read Kruger's article, the margins aren't small, they're negative...

[jetdriven]

The flutter limit can be raised 

[Seth]

I admit during a recent and first speed run in the Missile, where after a N E S W track my average groundspeed was 180 knots at 8000 feet, WOT 2450 RPM, I decended and realized I was at VNE - I pulled back some power, gently lowered my decent angle, and then gently spiraled down around some scattered clouds.  I was amazed how quickly my speed built up on the decent.

Take care,

-Seth

[Shadrach]

Quote: jetdriven

The flutter limit can be raised 

[jetdriven]

Because the M20TN flutter limit was raised higher than a M20K.  As far as his article goes, an RV-4 is an RV-4 is an RV-4. 

[Shadrach]

Quote: jetdriven

Because the M20TN flutter limit was raised higher than a M20K.  As far as his article goes, an RV-4 is an RV-4 is an RV-4.