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I'm having trouble with the aircraft busting the 250kt speed restriction under 10,000 feet.  Once the aircraft becomes airborne, the speed selection jumps to 235kts.  However, when the plane reaches around 6,000 feet, the speed selection goes to 275kts.  I usually reach that speed well before 10,000 feet.  What am I doing wrong in the TOGA config?  I even inserted a 250kt speed restriction under 10,000 feet into the FMC.  That didn't do anything.

Also, I've had a couple of occasions where I've engaged the TOGA switches on the takeoff roll. After the takeoff power is set and the airspeed is building, the throttles all of a sudden automatically go to idle.  What's that about?

Thanks! 

 

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There´s already a thread about it. It´s perfectly normal for the 747 that the calculated climb speed (in clean config) exceeds 250kts, even below 10000 feet.

 

Link to the thread: 

Best, Arne

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Full names here please Arne.

As mentioned by Arne, Rob, the Queen cannot climb safely in clean mode at 250 KIAS depending on weight, and the world's air traffic controllers know this and the regulations allow this.

As for your TOGA problem, you may need to take a look at your throttle options because it might be moving when in HOLD thrust mode, which will cause this to happen. See PMDG Options in the Introduction document.

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1 minute ago, downscc said:

Full names here please Arne.

As mentioned by Arne, Rob, the Queen cannot climb safely in clean mode at 250 KIAS depending on weight, and the world's air traffic controllers know this and the regulations allow this.

As for your TOGA problem, you may need to take a look at your throttle options because it might be moving when in HOLD thrust mode, which will cause this to happen. See PMDG Options in the Introduction document.

Hey Dan,

thanks for the heads up, but it´s in my signature...

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Hi,

When you climb through the acceleration altitude while in VNAV and speed box closed, the speed commanded by the FMS becomes the climb speed calculated according to the CI, the speed transition for 10000ft in the VNAV climb page (either Vref+100 or any speed coded for the deparure airport) or the first speed restriction on a waypoint which comes in the way whichever is lowest.

So to know what speed to expect during the climg:

_ Check your leg page once you have entered the departure (SID) for the speed restrictions

_ Check the VNAV climb page once you have completed the initialization of the FMC for the XXX/10000 speed transition > below the spd restr you can enter another speed restriction such as the 250/10000 which therefore will delete the calculated speed transition above.

_ Check the SEL SPD above the transition speed for the calculated climb speed.

During the climb the FMC will first adopt V2 + 10 as a target speed until the acceleration speed. Then the speed target becomes the speed transition or any speed restriction attached to a waypoint if lower until 10000ft. Above 10000ft, the target speed becomes either a speed restriction attached to a waypoint or the normal calculated climb speed.

If you are not sure about the speed the FMC will command, you can still takeover the speed control by push the IAS/Mach selector on the MCP which opens the speed box and let you enter the speed you want.
In your case, you may try to enter 250 when you see the speed increasing to 235kt. The aircraft will maintain the 250kt until you either push again the selector or you change the target.

 

If you want you can post screenshots of:

_ PFD and ND

_ Leg page and VNAV climb page of the CDU.

_ MCP

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There are a few aircraft that do this. MD90 at heavier weights can have a clean speed at 251 and up, and usually I'll fly 260, and no one notices. Perfectly alright! 

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ATC is very much aware of the speeds needed by heavy aircraft. I was never a big fan of the 250 below 10K anyway. That was created when jets and props were sharing ORD or LAX at the same time. Think 707 vs DC7.

 

Scott

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7 hours ago, skyymann said:

I was never a big fan of the 250 below 10K anyway. That was created when jets and props were sharing ORD or LAX at the same time. Think 707 vs DC7.

More and more airports implementing this rule whatever the airspace class is. I guess that at very airport with several runways used at the same time for takeoff and landing (such as LFPG with 2 rwys for takeoff and 2 for ldg.) And aircrafts taking off and landing every 2 minutes, it is safer to restrict the speed of the traffic in the crowdy lower airspace. If all these jets were departing and arriving at 300+ kts, I'm not sure the ATC could cope with the task.

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I even inserted a 250kt speed restriction under 10,000 feet into the FMC.  That didn't do anything.

Assuming you didn't press the Altitude button on the MCP to clear the restriction, I don't know how you busted your speed limit. As Romain says, we probably need more information. 

Speed set in window prior to takeoff? Transition altitude? Waypoint height/speed restrictions below 10,000', etc?

I think there used to be another reasons for limiting speed below 10,000 .... birdstrikes. However, if the flaps need to remain extended to keep the aircraft under 250kts, then flaps can be more susceptible to damage (still better than a windshield being shattered, though)

 

 

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What is your weight? Right around 630,000 pounds and up, the VNAV commanded speed will be above 250 knots. With the flaps up if you are going to 275 knots, you are probably pretty heavy, maybe around 830,000 pounds. This is normal and you want to advise ATC you require a "high speed climb". They know 747's going long haul are heavy and will expect and be given relief from exceeding 250 below 10,000. They will say "high speed approved" and more than likely ask what your speed will be in the climb for their planning purposes, if needed.

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44 minutes ago, Captain_Al said:

This is normal and you want to advise ATC you require a "high speed climb". They know 747's going long haul are heavy and will expect and be given relief from exceeding 250 below 10,000. They will say "high speed approved" and more than likely ask what your speed will be in the climb for their planning purposes, if needed.

Quick note for our FAA fliers:

The above quote does not pertain to the FAA realm. You already have a speed exemption under 91.117d, and you're expected (as noted in the 7110.65) to follow all aspects of 91.117 without reporting/broadcasting. This includes complying with the min safe speed of the aircraft, which may be above 250 (as specifically exempted in .117d).

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What is your weight? Right around 630,000 pounds and up, the VNAV commanded speed will be above 250 knots.

Robert (original poster) has already stated that he put a restriction of 250kts at 10,000 and the result was the same. Almost all of the respondents have ignored this statement. What he is describing is not normal.

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25 minutes ago, Qavion2 said:

Robert (original poster) has already stated that he put a restriction of 250kts at 10,000 and the result was the same. Almost all of the respondents have ignored this statement. What he is describing is not normal.

The FMS will not constraint speed in the case.

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4 minutes ago, downscc said:

You forgot that FMS speed constraints are AT OR ABOVE.

Hi Dan, 

It is the opposite: Speed constraint is assumed to be at or below the displayed speed.

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