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jpe828

Why are we not talking about this...

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If the density difference was enough to effect engine performance in a noticeable way you would expect it to also effect mixture and/or boost settings.

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It has been since 1984 that I sat in a left seat in a GA, but I have hand many, many right seat rides since, and as recently as a year ago. I do not recall anything like this in actual flight.

Perhaps the wind shifted.....


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No one cares?  Until now since you brought it up! 🙂

Edited by Manny
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Manny

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4 hours ago, bobcat999 said:

that is why, if you are in an airliner, you can feel the aircraft 'surge' as it enters the cloud, as the air is denser.

It's purely a visual effect. As a passenger you are momentarily getting the effect of something moving quickly across your field of vision. 

In real life, sitting in the office up front, i never noticed any effect on airspeed other than those which G550flyer mentioned, due to wind shear or crossing a sharp weather front with sudden temperature change.

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John B

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I was flying over a mountain area at 7000 feet with C172 when I got severe icing problems, my speed drop from about 100 knots to stall warning speed extremely fast, is that really realistic?


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4 hours ago, dilore said:

Since clouds are made of cotton one would expect a decrease in velocity.

...and a very soft landing in fog.

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Eric from EHAM, a flying Dutchman

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8 minutes ago, Ixoye said:

I was flying over a mountain area at 7000 feet with C172 when I got severe icing problems, my speed drop from about 100 knots to stall warning speed extremely fast, is that really realistic?

Yes.

The most frightened I've ever been was during icing encounters in non-icing certified aircraft.

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Richard Chafey

 

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8 minutes ago, Ixoye said:

I was flying over a mountain area at 7000 feet with C172 when I got severe icing problems, my speed drop from about 100 knots to stall warning speed extremely fast, is that really realistic?

Well, if your pitot tube is iced up then your airspeed could register it as though you are fairly rapidly losing speed (even though you are still flying at your original speed prior to the icing). That could be one explanation, ie. that it is simulating the failure of the ASI. Also, if you are in severe icing, your stall speed will increase dramatically, so you could stall at a relatively higher speed due to the airfoil issues that create substantial drag and loss of lift.

But I haven't been flying in cloud much in the sim so far so I'll check it out....does sound like people are reporting a pretty fast deceleration effect.


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4 hours ago, Johnny19 said:

So by this logic, a car would decelerate on the road when you enter low clouds or fog while driving. Clouds are not that dense to cause a slowdown of a moving object. 

Nope, in fact twice nope. In the real world at least, the aeroplane is not decelerating or accelerating in actuality, the pitot tube is detecting a different atmospheric pressure as it passes between dry and moisture saturated air, and so the ASI indication is changing. And a car doesn't use a pitot tube to measure its speed, it measures the speed from the rotation of the wheels and a small gear attached to a worm gear which turns a cable that is attached to the speedo needle and the odometer. 

But yeah, this is a real phenomenon incidentally, but like the icing visuals in MSFS, it is massively overdone to the point that it really shouldn't even be in a sim - it's more of an 'in a lab' phenomenon. In real life you'd never spot the change on an ASI needle in this circumstance.

But as an interesting aside, a pitot tube is indeed incredibly sensitive in reality. You can try this for yourself to see how sensitive to pressure changes a real pitot tube is if you have access to a small GA aeroplane with a speedo which is calibrated to a typical 100-ish knot range, and this is in fact how you test if a pitot tube is okay on a walkaround (if you have two people): Get the palm of your hand and place it gently over the opening end of the pitot tube and if someone watches the ASI whilst you do this, they will see the needle move a tiny bit even though you are only just barely altering pressure in the tube by covering it. This is also why you should never blow down a pitot tube, because they are sensitive enough to mean that such a sudden blast of air would probably damage the thing.

Edited by Chock
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Alan Bradbury

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1 minute ago, Purr said:

Well, if your pitot tube is iced up then your airspeed could register it as though you are fairly rapidly losing speed (even though you are still flying at your original speed prior to the icing). That could be one explanation, ie. that it is simulating the failure of the ASI. Also, if you are in severe icing, your stall speed will increase dramatically, so you could stall at a relatively higher speed due to the airfoil issues that create substantial drag and loss of lift.

But I haven't been flying in cloud much in the sim so far so I'll check it out....does sound like people are reporting a pretty fast deceleration effect.

No, the speed drop was real, to about 40-45 knots, I barely crossed the mountain with my life intact.


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I raised that issue during alpha/beta testing didn't gain any support. Clouds do not affect your performance, turbulence does . But still turbulence invoke man made adjustments to the power which in turn affect performance.

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flight sim addict, airplane owner, CFI

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10 kts of airspeed? That's like extending the gear. To have this on entering a cloud is totally bogus.


David Porrett

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I have only seen aircraft performance affected twice while in clouds:

1. Went into some clouds over DC in the middle of the night. Instantly you can hear rain pounding the windscreen as we were being tossed around. I saw the N1s on all three engines start to decrease a couple percentages and I threw on continuous ignition. 

2. On a short hop from Bogota to Panama City, we hit some clouds at cruise altitude. We suddenly heard ice pelting all over and then the auto throttles kicked off and some blue and amber CAS messages populated with the usual bongs. There were SAT messages on the MCDUs and engine back up data and TAT messages were in the stack. A few seconds later we exited the clouds and all the messages went away. We flew through a hot tower and the TATs iced up faster than the TAT probe could be de-iced.

You normally won't notice anything besides the bumps when there isn't any precip in them.   

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3 minutes ago, DavidP said:

10 kts of airspeed? That's like extending the gear. To have this on entering a cloud is totally bogus.

Yup. The only clouds which really slow you down are the ones with granite in the middle of them.

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Alan Bradbury

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Didn't meant to trigger with a "clickbait" title, genuinely curious why no one is talking about this. There is no explanation. It is a problem with the sim...I am a real world pilot, have flown many GA airplanes in IMC... it does not effect airspeed. My point was, I am surprised this hasn't been raised more (at least I have not seen it). It is annoying! When flying in a sustained cloud layer the other day, I was 10 knots slower over the ground. Coming out of the layer, my speed shot up.

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