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Fatback

Flying below 250kts while heavy

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The VA that I fly for has made the 250kts under 10k rule applicable to all flights, regardless of aircraft type or minimum safe airspeed. I have just started flying the MD-11 and have come across a long haul route out of MPTO with a SID that has a fairly long distance to fly holding at 5000 ft. It seems like I'm burning a lot of fuel and maintaining a high N1 with flaps 28 but if I retract them they go to 0, no intermediate steps, and the FMC automatically compensates and the FMC commanded speed goes above 250kts even though I have a speed restriction programmed into it. If I go to the DAF and put in 15 flaps I can then retract the flaps and extend them again to 15 quickly and the FMC speed stays below 250kts. So I'm wondering whether it's proper procedure to leave flaps at 28 and let the engines scream or switch to the DAF screen, change the DAF settings to flaps 15, go back to the main screen and retract and then extend flaps so they're at 15. 

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So I'm wondering whether it's proper procedure to leave flaps at 28 and let the engines scream or switch to the DAF screen, change the DAF settings to flaps 15, go back to the main screen and retract and then extend flaps so they're at 15.

 

I'd honestly tell your VA to get with the program and create an exception for heavy aircraft before I tried to completely alter my own behavior.

 

Why are you at Flap 28 on departure anyway?  The max for departure should be in the DAF range, if I'm not mistaken.

 

You can use a DAF value low enough to leave the flaps out, or I think you could probably get away with just Flap 0 / Slats extended.  Whatever you do, though, don't retract, change the DAF and extend them again.  That's a lot of extra "wear" on your hydraulics, and is not something that anyone would recommend, honestly.

 

 

 

...but again, I'd go after the VA for an unrealistic practice.  No sense in trying to bend your simming to backwards "realism."

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Unless your VA changes their mind, you have two reasonable options:

 

1) lower your takeoff weight until the FMS calculates a lower climb speed under 250kts, or 

2) retract flaps/slats as scheduled and push your speed knob when you reach 240kts; this will hold your speed under 250kts; then push FMS speed to resume optimal speed when legal.

 

Unless there is an emergency, you want to clean up as soon possible after takeoff and stay clean until your final descent.

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My bad, I meant to say flaps 22 on departure. It's a long haul so lowering my takeoff weight is not an option. If I takeoff with a lower flap setting than recommended or no flaps at all isn't there a safety issue? 

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I'm surprised this thread hasn't gone south already... VA "realism" purist are known to come with torches and pitchforks after anyone citing real world experience or quoting the FAR and other ICAO regulations that clearly state it's perfectly possible for heavy A/C to be cleared by ATC to "break" the 250 under 10k.

 

Wearing Flamesuit... checked.

 

regards

-E

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If I takeoff with a lower flap setting than recommended or no flaps at all isn't there a safety issue?

 

No.

 

If you're referring to TOPCAT's OPTIMUM or RECOMMENDED setting, it's only an optimal setting based off of the information TOPCAT has.  If you change the value in TOPCAT to whatever setting you want to use, as long as you run the numbers and TOPCAT doesn't throw error messages at you, then you're safe.

 

TOPCAT only knows so much.  If you need another flap setting, then you have to tell it.  It'll tell you if that works for the runway in question (which, in many cases will be just fine).

 

 

 


VA "realism" purist are known to come with torches and pitchforks after anyone citing real world experience or quoting the FAR and other ICAO regulations that clearly state it's perfectly possible for heavy A/C to be cleared by ATC to "break" the 250 under 10k.

 

Don't worry.  It's still early, and I'm ready. :wink:

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My bad, I meant to say flaps 22 on departure. It's a long haul so lowering my takeoff weight is not an option. If I takeoff with a lower flap setting than recommended or no flaps at all isn't there a safety issue? 

 

So let's summarize:

  • can't exceed 250kts
  • won't reduce cargo (always an option) or fuel/route
  • won't use the speed knob override to hold your speed at 240kts for a few minutes.

 

Something has to give.  Leave your takeoff flaps choice alone; its not the problem here.

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It's just a simulator, nobody will come knocking at your door with your pink slip because you busted a non existant limit. Or just lower your "cargo" which is really just a set of numbers in a computer program that affect virtually nothing in real terms.

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So let's summarize:
can't exceed 250kts
won't reduce cargo (always an option) or fuel/route
won't use the speed knob override to hold your speed at 240kts for a few minutes.

 

Clark, good summary. I can't exceed 250kts as that is our airline SOP and reducing cargo (meaning passengers in this context) is out and as the route is fixed I can't very well shorten it or reduce the amount of fuel I have on board for takeoff. The speed knob seems to be the only option if I'm not going to be at flaps 22. But then what is the point of having a Minimum Safe Airspeed if I'm just going to fly it at 245kts anyway? Maybe it's just best to leave it at flaps 22 and plow through the hold at 5000 ft until I can I can resume my ascent and get to 10000 feet?

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Why can you not reduce payload? To be honest If I was you I would be looking for another VA.. Sounds like the rules where made up by a 13 year kid striving for realism when he has no idea what real is.

 

 

Edit - Also wondering what SID you are talking about? am looking at my charts for Panama and can't see it, curious as to why you have to enter a hold.

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Why can you not reduce payload? To be honest If I was you I would be looking for another VA.. Sounds like the rules where made up by a 13 year kid striving for realism when he has no idea what real is.

 

My thoughts exactly.

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Clark, good summary. I can't exceed 250kts as that is our airline SOP and reducing cargo (meaning passengers in this context) is out and as the route is fixed I can't very well shorten it or reduce the amount of fuel I have on board for takeoff. The speed knob seems to be the only option if I'm not going to be at flaps 22. But then what is the point of having a Minimum Safe Airspeed if I'm just going to fly it at 245kts anyway? Maybe it's just best to leave it at flaps 22 and plow through the hold at 5000 ft until I can I can resume my ascent and get to 10000 feet?

 

Sorry, let me be clearer.  By the time you get to 5000' / 240kts your flaps/slats should be up.  Their purpose is to help you quickly get above the birds and abatements by helping you climb steeply.  Above about 2000' AGL the plane wants to get faster to climb faster (not steeply) so it wants to be clean.  Your speed limit problem deals with the departure/climb phase, and the FMS pre-calculated goal of Vcl.

 

Vcl is calculated by the FMS to give you an optimal performance during the climb phase based on your take off weight; it is not a requirement.  You are not doing anything wrong, unusual or unsafe by pushing the speed knob to hold off acceleration for a little while.  

 

This is a good exercise of interacting with the automation to adapt to a local situation.  Try to have fun with it.  Even if your VA did not have this policy, any local ATC might so it's good practice.

 

Cheers

 

(PS I looked up departures for Panama City and did not see any requirements to hold at 5000'.  You might want to double check that; or tell me I missed it. :)

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I'm surprised this thread hasn't gone south already... VA "realism" purist are known to come with torches and pitchforks after anyone citing real world experience or quoting the FAR and other ICAO regulations that clearly state it's perfectly possible for heavy A/C to be cleared by ATC to "break" the 250 under 10k.

 

Wearing Flamesuit... checked.

 

regards

-E

Can you please provide the FAR PART that you are referring to? Because that I know of acft are designed with the 250kts below 10K in mind. No matter how heavy. Only the Administrator can clear an acft to go faster than 250kts below 10K, ATC can't.

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Thanks for the detailed post Clark, it's going to take me a few minutes to absorb it. The departure is the EGET1B from rwy 03L and I'm sorry, it's not a hold at 5000' it's an altitude restriction of 5000' but 30 miles from the airport, so effectively a hold until I pass that waypoint.


Can you please provide the FAR PART that you are referring to? Because that I know of acft are designed with the 250kts below 10K in mind. No matter how heavy. Only the Administrator can clear an acft to go faster than 250kts below 10K, ATC can't.

 

Reik, here it is. Look at paragraph D. No approval is necessary to go above 250kts if your clean minimum airspeed is higher because it is allowed by FAR regulation. Normally pilots will inform ATC, but that is a courtesy not a requirement. 

 

Sec. 91.117 — Aircraft speed.

a: Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).

 

b: Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.

 

c: No person may operate an aircraft in the airspace underlying a Class B airspace area designated for an airport or in a VFR corridor designated through such a Class B airspace area, at an indicated airspeed of more than 200 knots (230 mph).

 

d: If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.

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