G7USL

Positive Rate?

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What are the requirements criteria for the call 'Positive Rate'?

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I would think when you're taking off and you've established a positive rate of climb.

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1 hour ago, G7USL said:

What are the requirements criteria for the call 'Positive Rate'?

don't overthink this...

ithe requirements are when you have a positive rate of climb.

uusually an indication from the VSI

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Yeah, positive rate is based on the VSI.  It can't be based visually as the sensations of flight can be misleading.

 

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On most airlines, it is typically that the PNF makes that callout when there are two indications of a climb, these being the VSI and the altimeter. It differs on Boeings to Airbuses, one SOP says use the phrase 'positive rate', the other says use 'positive climb', but personally I sing this instead, as it is far more fun lol: https://en.wikipedia.org/wiki/The_U.S._Air_Force_(song)

Since it is the PNF that makes the call, that's kind of ironic, because if the PNF is in the right seat, it's actually the altimeter on the left seat instruments which sends the transponder altitude data to ATC scopes lol.

But really, one should not rely too much on the VSI's reading, since it gives pretty much an 'instantaneous' reading of what the aircraft is doing, thus it can potentially indicate you are climbing when you might simply have hit a minor bit of turbulence or bump on the runway which bumped you up off the runway for a second or so; you could still then settle back down onto the runway (same with the radar altimeter as well, especially since the sensor for th RA is right at the rear of the aircraft, where it will be affected by being far from the pivot point of the main gear and would actually show a descent when you rotated lol).

The altimeter is a far better indicator for a true positive rate of climb, because it works off air pressure from the static port, so it has a bit of lag in displaying a climb, which means if you see your altimeter needle indicating a decent climb, you really are going up at a positive rate.

So long as you are nowhere near Vle (maximum gear down speed), then there is no rush to give the callout (personally, I'd say give it at least 100-150 feet altimeter indication before making the call; it's better to be safe than sorry by trying to be cool and get the gear up the moment you lift off, because if you settle back onto the runway with the downlocks off, your career as an airline pilot is probably going to be over.

In other words, the reading on the VSI might say you are going up, but the needle on the altimeter actually means you are going up!

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3 hours ago, Chock said:

On most airlines, it is typically that the PNF makes that callout when there are two indications of a climb, these being the VSI and the altimeter. It differs on Boeings to Airbuses, one SOP says use the phrase 'positive rate', the other says use 'positive climb', but personally I sing this instead, as it is far more fun lol: https://en.wikipedia.org/wiki/The_U.S._Air_Force_(song)

Since it is the PNF that makes the call, that's kind of ironic, because if the PNF is in the right seat, it's actually the altimeter on the left seat instruments which sends the transponder altitude data to ATC scopes lol.

But really, one should not rely too much on the VSI's reading, since it gives pretty much an 'instantaneous' reading of what the aircraft is doing, thus it can potentially indicate you are climbing when you might simply have hit a minor bit of turbulence or bump on the runway which bumped you up off the runway for a second or so; you could still then settle back down onto the runway (same with the radar altimeter as well, especially since the sensor for th RA is right at the rear of the aircraft, where it will be affected by being far from the pivot point of the main gear and would actually show a descent when you rotated lol).

The altimeter is a far better indicator for a true positive rate of climb, because it works off air pressure from the static port, so it has a bit of lag in displaying a climb, which means if you see your altimeter needle indicating a decent climb, you really are going up at a positive rate.

So long as you are nowhere near Vle (maximum gear down speed), then there is no rush to give the callout (personally, I'd say give it at least 100-150 feet altimeter indication before making the call; it's better to be safe than sorry by trying to be cool and get the gear up the moment you lift off, because if you settle back onto the runway with the downlocks off, your career as an airline pilot is probably going to be over.

In other words, the reading on the VSI might say you are going up, but the needle on the altimeter actually means you are going up!

 

As Chock said the procedure during T/O is two positive indications.  Both the Altimeter and VVI must indicate a CLIMBING trend to be considered Positive Climb.  VVI will show positive before the aircraft leaves the ground and Altimeter alone could have you sinking back to the ground.  It takes both to be certain as to whether or not you are in fact climbing away.  Per Boeing and my companies FCOM

Condition: When both the Altimeter and Vertical Speed displays show a positive rate of climb and airspeed above V2

Callout [PM] unless noted:  “Positive climb”

                                                “Gear up” [PF]

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6 hours ago, Chock said:

(same with the radar altimeter as well, especially since the sensor for the RA is right at the rear of the aircraft, where it will be affected by being far from the pivot point of the main gear and would actually show a descent when you rotated lol).

Which aircraft, Alan? 

:wink:

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25 minutes ago, Qavion2 said:

Which aircraft, Alan? 

:wink:

It differs between aircraft, but it is very often behind the main wheels, since that is more useful when the aircraft is flaring on landing, where the arse end of the aeroplane is obviously lower down, since you want to know which bit of the aeroplane is nearest the ground when using it to judge a landing. It is easier to calibrate for the best average readings because of that.

However, it's not always located at the back, for example it is slightly in front of the main wheels on Boeing 757 and calibrated to indicate a reading as though it is located where the main wheels are. Aeroplane manufacturers would ideally like to put the antenna right in between the main wheels, but they can't do that, because its signal would be interfered with by the presence of the main gear when lowered, so manufacturers try to put it at least near the main wheels if they can. As noted, they are calibrated to allow for some of the fact that they are not physically right near the main wheels, but that does mean they do show some bizarre readings on occasion in spite of calibration, for example, a CRJ has its antenna near the back and will display a negative value on rotation for take off, since it is calibrated to read zero when the thing is sitting level on the ground.

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It's not just a question of sticking the nose up. As that will be indicated on the instruments too. In fact over rotation can cause the wings to stall and you never actually leave the ground. You should never call "postive rate" until past screen height. That ensures the "whole aircraft is airborne.

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Positive rate is indication of a climb: 

Your VSI is positive indicating like 100, 200 ft or more + your Altitude indicator show you are gaining altitude...

 

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Interesting how many different procedures for this call are thrown in here.
Let me add one more based on what I learned at flight school:

The VSI always lags behind a little bit so you can already be in a positive climb while the VSI still indicates zero.
Typically in big jets this is somewhat reduced with some modern techniques, but it is still quite visible.
The altimeter is more accurate, thus where I learned you call positive rate based on a climbing altimeter indication only, ignoring the VSI.

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4 hours ago, Chock said:

However, it's not always located at the back, for example it is slightly in front of the main wheels on Boeing 757

And on 737s, 767s, 747-400s, 777 and (all but 1 type of) Classic 747. Airbus seem to have a preference for putting them behind the gear.

They're all calibrated for a certain pitch angle, gear strut extension, bogey tilt, etc. On the 777, they're not far behind the nose gear. On the 747-400, they're just behind the second cabin door. I see some advantage in having them relatively close to the gear, but given a choice of in front or behind, I'd rather have an early warning that my nose was going to touch down before my tail :laugh:

Cheers

 

P.S. And 787

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