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ryanbatcund

Too Dangerous?

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Is there a danger flying so close to MMO?

 

I really like to go fast hehe

 

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Is there a danger flying so close to MMO?

 

Seems to me it is a question of how 'real world' you want to be.  The aircraft has been certified up to Mmo. If you fly AT Mmo and an unexpected event (turbulence, etc) causes Mmo to be exceeded, you are now flying outside the certification envelope, not a good thing in the RW I would assume. Some aircraft have built in Mmo protection, such as an automatic pitch up to reduce speed if Mmo is exceeded.

 

The Lear35 manual says: VMO/MMO shall not be deliberately exceeded in any regime of flight (climb, cruise or descent) unless a higher speed is authorized for flight test.

So I don't think the wings will immediate come off if you should 'accidentally' exceed Mmo a bit.  RW speaking, however, it just doesn't strike me as smart to push the certification envelope boundaries.

 

I'm sure someone with RW experience in jet a/c can provide a better answer.

 

Al

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If you exceed MMO by .01 Mach, you will get the overspeed audible warning. An additional .01 Mach above that point (about Mach 0.83), and the "stick puller" will activate, causing a rather abrupt pitch up.

 

Testing the Mach overspeed warning and protection is required every 24 months on a Lear 35, using an air data test set.

 

Though many T-tail business jets have a stick PUSHER, to prevent a full stall when flying too slowly, not all jet aircraft have a stick puller. It was required on Lear 20/30/50 series aircraft due to their susceptibility to Mach tuck, which can cause a sudden violent pitch down, (and possible unrecoverable loss of control) when exceeding MMO.

 

Not sure if the puller is simulated in this product though.

 

You could prevent the puller from activating by turning off the Mach trim system, but if you do that, you will get the overspeed audible alarm at Mach 0.73!

 

Another maintenance requirement concerns the leading edge fairings. If any leading edge fairing is removed for maintenance, and reinstalled, the aircraft cannot be returned to service until the aircraft has had a full-stall flight test, which can ONLY (legally) be done by a certified Bombardier/Learjet factory test pilot. In addition to the pilot's fee for performing the stall test flight, the operator is required to pay for the test pilot's airfare and per diem expenses.

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At least one (RW) pilot has bragged online of flying close to redline. 

 

"We don't have autothrottles in the Ultra, so during long cruise legs it's fun to try to get the speed right up to redline manually, without going over - our plane will overspeed in cruise if we set the throttles to maximum continuous thrust.  Our maximum Mach is 0.755, so I'm about 6/10ths of a knot from setting off the overspeed alarm. "

 

http://sulako.blogspot.com.mt/search?updated-max=2013-01-17T14:27:00-05:00&max-results=15

 

And I'm sure there are more.

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Mmo is the maximum certified speed so you *can* fly at Mmo. Nobody will prevent you from doing it.
 

What I say now is pure theory, myself I would never do this (but I know others did):

Certification demands a safety margin above Mmo which the plane has to demonstrate during testflight. So it won't brake up if you exceed Mmo and take immediate corrective actions.

Never try this in real flight though!

For the sake of flight simulation: Go for it.

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Guys, as far as wing structural integrity goes, there is a safety margin to ensure no structural damage (not even breakage, but plastic deformation) up to 1.5x past the aircraft operating limits. That includes G loading, aerodynamic forces, and fluid-structure integration phenomena (torsion divergence, control reversal, and aerodynamic flutter). So you are not allowed to go past it but if you accidentally do, you will not damage the plane structurally. Bear in mind manufacturer doesn't guarantee stability and control above VNE/MMO. Now, when you get really close to mach 1, wing center of pressure shifts aft making airplanes increasingly stable, but also causing strong nose down moment in aircraft not designed for supersonic operation.

 

So the puller is there to prevent you from going faster than you can actually control the plane. In most civil aircraft, you don't even have enough engine power to cause structural damage in level flight through overspeed, providing you can maintain flight control at that airspeed.

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I only sim close to mmo in various aircraft at cruise altitude with winds aloft turned off in FSX:SE. One dodgy METAR input or weather update and BANG: Instant change from 50 kt tailwind to 50kt headwind = crash with no chance to alleviate an overspeed of such magnitude. :(

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Hey Ryan,

 

I can get the wing supersonic but I can't break the sound barrier.  Go high, say FL510, turn down the sound so the overspeed alarm won't wake up the kid, and start with about a 10 degree descent angle and hold the N1 to something in the 90s and you can exceed Mach 0.925.  Really.

 

I don't think you could tear the wings off one of these early Lears.  8 Spars, come on.  Just no wild maneuvers, Fly Fast, Fly Jets.

 

Regards,

 

Ray

 

Is there a danger flying so close to MMO?

 

I really like to go fast hehe

Ryan,

 

None whatsoever. Unless you get so excited that you fall out of your chair!

 

I fly at M 0.0825 - 0.827 often. I also add enough tailwind to keep my GS around 500kts.

 

Yesterday I was cruising at FL510 along the East Coast. I recorded these numbers. -26 TAT, N1 100.5, ITT 327, 197 TAS, M 0.827, FF 1053 Lbs. I was carrying 48% fuel remaining. I use the 'Corrected N1 numbers' so I can fly the Citations at full power for cruise.

 

Have Fun, Fly Jets, Fly Fast.

 

Regards,

 

Ray

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I don't think you could tear the wings off one of these early Lears. 8 Spars, come on. Just no wild maneuvers, Fly Fast, Fly Jets.

In fsx, no, in real life, aeroelasticity will tear them off at some point :D

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