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Minimum Safe Manoeuvering Speed


Ned Gravel

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24 minutes ago, Hank said:

Most of my takeoffs are no flaps, unless I'm heavy or the field is short (like 2000'). Gear is stowed by treetop level, all that drag just slows the climb. From a previous discussion, here are pictures of my typical trim positions:

 

My main point is there are always two things that come into play in abnormal situations.  Surprise and recognition.  Typically it takes two seconds to understand and accept what is happening... then reaction comes.  It's those few seconds of keeping the nose up that can kill.  If unloading the wing is trained as an automatic response to any loss of thrust or aircraft upset, your chances of a successful outcome increase dramatically.   I like stacking the odds in my favor.

One thing I learned today:  I can and do induce control inputs (namely rudder) without knowing it.  The sim keeps track of that stuff.  I mention it because most don't have the benefit of screwing up in a level D simulator.  In a high-stress, high-AOA situation, there is a good chance you will be pushing the rudder, unbeknownst to you, and accelerating the stall of one wing.  

I am always looking for ways to make my GA flying as close to as safe as my heavy iron flying.  I love discussions like this for that reason.


 

Edited by Guitarmaster
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P.S.--with nearly full down trim in level cruise, you have a significant down thrust vector. Yanking the throttle to idle (or selectig a dead magneto) would theoretically create an upward vector, but we definitely experienced an immediate, strong downward motion of the nose.

I'm really not trying to be difficult, just applying my Mechanical Engineering education and experience these last few decades to try to understand how idling the throttle creates an upward vector when climbing but a downward vector when cruising. 

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2 minutes ago, Hank said:

P.S.--with nearly full down trim in level cruise, you have a significant down thrust vector. Yanking the throttle to idle (or selectig a dead magneto) would theoretically create an upward vector, but we definitely experienced an immediate, strong downward motion of the nose.

I'm really not trying to be difficult, just applying my Mechanical Engineering education and experience these last few decades to try to understand how idling the throttle creates an upward vector when climbing but a downward vector when cruising. 

Not being difficult at all :)  I love these discussions.  

I think it's just a matter of velocity.  I would bet, if there was an accelerometer in the plane, when the engine quit, everything else being equal,  there would be a very momentary pitch-up, however slight, before the stronger forces overcame it.  I don't have the numbers, but the thrust line is probably around 3 degrees downward.  Maybe a fun study for the engineering types (not me) to figure out the force vectors surrounding the airplane in slow flight and cruise.  I'm sure it can be quantified mathematically.... I was told there would be no math however  :)

In the end, It always amazes me how fast the airspeed bleeds and how strong the natural tendency is to pull-up when close to the ground.  Add a distraction and it can go south very quickly.  By aggressively unloading the wing, the stall risk is automatically brought to nearly zero and gives you precious seconds to evaluate and respond to the situation.  The nose can always be raised if all is looking good.  

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I am not very good at math.    But I suggest you go up and try it.   In whatever they were flying in the video 4 seconds was too long.    Like they were doing Feel light in the seat type of push over.

This was kind of fun

https://www.boldmethod.com/cfi-tools/forces-in-a-climb-or-descent/

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9 hours ago, ArtVandelay said:

I think best glide speed would be better, gives margin of error for a 40° bank and of course in case of an engine out is what you want anyway.

We don’t need to memorize another speed.

 

Tom

 

I agree with you about max gross best glide covering it in a single. I will add that in every single I have flown, a bit over 30 makes and models, best glide is ballparked with a level pitch attitude - the familiar one we use in cruise. If you watch the video closely, you will see that this is pretty much what is going on in both the power loss and go-around scenarios. Power gone, pitch to level. Don't even need an ASI. 

 

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On 9/22/2019 at 9:44 PM, Guitarmaster said:

Not being difficult at all :)  I love these discussions.  

I think it's just a matter of velocity.  I would bet, if there was an accelerometer in the plane, when the engine quit, everything else being equal,  there would be a very momentary pitch-up, however slight, before the stronger forces overcame it.  I don't have the numbers, but the thrust line is probably around 3 degrees downward.  Maybe a fun study for the engineering types (not me) to figure out the force vectors surrounding the airplane in slow flight and cruise.  I'm sure it can be quantified mathematically.... I was told there would be no math however  :)

In the end, It always amazes me how fast the airspeed bleeds and how strong the natural tendency is to pull-up when close to the ground.  Add a distraction and it can go south very quickly.  By aggressively unloading the wing, the stall risk is automatically brought to nearly zero and gives you precious seconds to evaluate and respond to the situation.  The nose can always be raised if all is looking good.  

Personally I always smile when people say Mooney’s are “hard” to slow down.  Remove power and pitch up and they DEFINITELY SLOW DOWN.  I do this often to get to gear extend after decent.

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You can lose 70-80 mph of IAS  in 3 miles, Just by leveling off and setting the power to 20 inches. As it slows pull back a little more to like 17. As it slows  it wants to pitch over and not slow  down until you actually hold altitude for a bit. 

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3 minutes ago, RogueOne said:

Personally I always smile when people say Mooney’s are “hard” to slow down.  Remove power and pitch up and they DEFINITELY SLOW DOWN.  I do this often to get to gear extend after decent.

It's all relative, though.  I've been sitting in the back as a passenger with my wife's flying lessons in an Archer, and my arms and legs get tired because she tends to approach too high, and psychologically I'm pushing a nonexistent yoke and rudder pedals, and pulling a nonexistent throttle, trying to get us down.  Then when she finally pulls power, it seems like the plane drops like a rock the final 500 feet.

We have to get the whole "stabilized approach" thing still, obviously :rolleyes:

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9 hours ago, RogueOne said:

Personally I always smile when people say Mooney’s are “hard” to slow down.  Remove power and pitch up and they DEFINITELY SLOW DOWN.  I do this often to get to gear extend after decent.

I've overflown a field hiding behind a ridge at 2000-2500 agl in a Slowhawk, pulled throttle and entered downwind. In my mighty M20-C, Approach used to keep me 4000'agl until 4nm from the field; I'd pull throttle, deviate several miles east, make a descending 540° turn then decelerate west to join downwind for 26.

So yes, Mooneys do slow down. And yes, Mooneys do descend. What they do not do well is lose airspeed while descending.

Kind of like my '17 Altima doesn't lose speed when I take my foot off the gas nearly as quick as my '04 Ranger does. In comparison, the car hardly slows at all . . . . Just like my Mooney hardly slows in comparison to a Cessna.

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14 hours ago, jaylw314 said:

It's all relative, though.  I've been sitting in the back as a passenger with my wife's flying lessons in an Archer, and my arms and legs get tired because she tends to approach too high, and psychologically I'm pushing a nonexistent yoke and rudder pedals, and pulling a nonexistent throttle, trying to get us down.  Then when she finally pulls power, it seems like the plane drops like a rock the final 500 feet.

We have to get the whole "stabilized approach" thing still, obviously :rolleyes:

With new pilots, a common thread is being used to a car and how quickly is slows and how tight it turns. Anticipation and "being ahead of the airplane" are learned skills. And once we learn it at the primary level, the lesson ends up being model-specific and needs to be relearned when we step up to something faster. Doesn't have to be a Mooney. I've seen it with as "dirty" an airplane as a Cutlass with good Skyhawk pilots.

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On 9/22/2019 at 5:29 PM, Guitarmaster said:

Many get killed in a twin for the EXACT reason they do in a single.  The industry calls it a Vmc roll, but it's really nothing more than exceeding crossover AOA.  In a single, it results in a spin; the twin has another engine to help you over the top.  The solution is exactly the same as a single: push forward until the airspeed increases to AT LEAST Vmc, but I like to see Vyse before climbing... and pushing forward that close to the ground is really hard to do.

Interesting point. For those not familiar, Vmc is the speed below which you run out of rudder authority to counteract a yaw produced by asymmetric thrust. Crossover speed is the speed below which you run out of lateral control authority to counteract a rudder hard over. Crossover speed is related to AOA in the sense that at high AOA the wing is operating at a high lift coefficient and the ability of the aileron to further increase CL to raise a wing is impaired. A roll caused by loss of an engine below Vmc in a piston twin can be counteracted by reducing power on the operating engine slightly which decreases Vmc. But, that's also really hard to do when close to the ground.

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