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Harald Huber

777 VLS too Low for the weight

42 posts in this topic

The picture will explain it better than me, but basically what happens is that during approach with 242 tons in the following picture, VLS is around 100 knots, for a 777 is very low, anyone else having the same issue?

 

I use P3d V4.

19390649_10154692839293059_4380332344198

 

 

Also I am having issues with the Radio Altimeter Callouts, they are based on the runway elevation, not on the actual RA readout. 

 

 

Regards!

 

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41 minutes ago, Harald Huber said:

The picture will explain it better than me, but basically what happens is that during approach with 242 tons in the following picture, VLS is around 100 knots, for a 777 is very low, anyone else having the same issue?

Willing to bet you gave it KGs when it was expecting LBS. Be mindful of the units used for the livery you're flying.

41 minutes ago, Harald Huber said:

Also I am having issues with the Radio Altimeter Callouts, they are based on the runway elevation, not on the actual RA readout. 

They're not radio altimeter callouts. They're GPWS callouts. This distinction is important because some are actual BARO and some are RADIO.

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It's in KG, flying the Freighter. That's why it makes no sense to me.

 

And does the actual 777 give RA callouts based on BARO? I fly Airbuses and they issue the Callout based on actual RA not BARO (GPWS). 

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The fuel weight is in pounds.

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Please clarify, I read KGS on EICAS. This is a picture of the 747 in KGS and I have the exact same issue

 

19388438_10154693385308059_4965919095503

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Yup, my bad.  I was trying too hard to read that in the previous photo.

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The only explanation for this is either a) you've set up the aircraft incorrectly (we've ruled out units, maybe double check your procedure), or b) an external program like weather is causing this.

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Based on the approach attitude, thrust setting and Vapp speed, it is exactly what you expect on the 777 at this weight. 

So the answer is YES, at 240tons, the Vmms (VLs) of 100kts is a bit low for this weight. Normally Vref is usually about 15-10kts higher than Vmms. Based on the FCTM the  Vmms is 1.3x Stall speed with flap down.

So I would expect to see something around ~135kts - 140kts, and not at the bottom of the speed scale. unless Vref is artificially raised to maintain adequate Vmca margin in the event of an engine failure in a Go Around (as far as i understand only the 77LR has this feature). But at 240tons, this is likely not the the case here with the 777LR, because according to Boeing, the Vmca will only fall below stick shaker speed when the weight is ~211tons or below. 

 

 

 

 

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4 hours ago, Driverab330 said:

Based on the approach attitude, thrust setting and Vapp speed, it is exactly what you expect on the 777 at this weight. 

So the answer is YES, at 240tons, the Vmms (VLs) of 100kts is a bit low for this weight. Normally Vref is usually about 15-10kts higher than Vmms. Based on the FCTM the  Vmms is 1.3x Stall speed with flap down.

So I would expect to see something around ~135kts - 140kts, and not at the bottom of the speed scale. unless Vref is artificially raised to maintain adequate Vmca margin in the event of an engine failure in a Go Around (as far as i understand only the 77LR has this feature). But at 240tons, this is likely not the the case here with the 777LR, because according to Boeing, the Vmca will only fall below stick shaker speed when the weight is ~211tons or below. 

 

 

 

 

Nice answer, since I fly the A320, I am used to see 5 knots difference between Vls and Vapp. 

 

thanks for that!

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:biggrin:  You are welcome 

I do miss the term Vls and Green Dot and the beloved airbus FM. 

 

My fd who flies the A350 is enjoying it very much. Too bad my company is not offering any Boeing to airbus converison at the moment.

I would love to go have a try one day before retirement. 

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For your info, this is what you would expect to see. 

https://ibb.co/iecNCk

Picture taken from a Boeing certified ground training device called the IPT (Integrate Procedure Trainer). The airplane type of the IPT is a 777-300 with RR engine, but the speed margin is very similar to the 773ER / 77LR but at a slightly lighter weight (~233tons). 

In the IPT, I was practicing the procedure of doing the RNP 13L approach into JFK. 

Note: the top of the Vmms does not vary with G load. 

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2 hours ago, Driverab330 said:

For your info, this is what you would expect to see. 

https://ibb.co/iecNCk

Picture taken from a Boeing certified ground training device called the IPT (Integrate Procedure Trainer). The airplane type of the IPT is a 777-300 with RR engine, but the speed margin is very similar to the 773ER / 77LR but at a slightly lighter weight (~233tons). 

In the IPT, I was practicing the procedure of doing the RNP 13L approach into JFK. 

Note: the top of the Vmms does not vary with G load. 

So basically I am right then? It is a bug?

 

And I would love to switch from Airbus to Boeing haha

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16 minutes ago, Harald Huber said:

So basically I am right then? It is a bug?

 

And I would love to switch from Airbus to Boeing haha

Hmmm... I cannot say it's a bug, but it is certainly not what I will expect to see on the real airplane. 

Perhaps you should raise to issue to one by submitting a ticket in the PMDG website. 

Talking about airbus to Boeing conversion, once you have jumped across to the Boeing you would miss two things 1) the table and 2) the FMC :laugh:

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Just now, Driverab330 said:

Hmmm... I cannot say it's a bug, but it is certainly not what I will expect to see on the real airplane. 

Perhaps you should raise to issue to one by submitting a ticket in the PMDG website. 

Talking about airbus to Boeing conversion, once you have jumped across to the Boeing you would miss two things 1) the table and 2) the FMC :laugh:

haha I get your point, still I would love to fly Boeing.

 

And I already raised the ticket, still no answer. :huh:

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