Can't seem to loss speed even with the Spoilers out with AS2012

[nrcrate 40]

I agree with the gist of what you are saying, but just curious where did the " but you can summerise it to only required between -10 and +10 below 10k with visible moisture present. It increases idle and reduces available power " come from?

I'm not quite sure where the confusion is- he's stating a good rule of thumb for anti-ice usage. For example, here's a quote from a nice AOPA icing brochure:

Icing is most likely to occur when:

• The outside air temperature (OAT) is between 0ºC

and -20ºC, but the worst icing will usually occur

between 0ºC and -10ºC.

• If the temperature dew point spread is fewer than

2ºC and the temperatures are between 0ºC and

-20ºC be especially vigilant for ice.

• The worst icing is common in the top 1,000 feet of

cumulus clouds when the temperature is 0ºC or

lower.

And the visible moisture is a given with a dewpoint spread of less than 2ºC.

[Daveng3 0]

Hi Nick,

 

I thought the posting is refering to the 737NG or any IFR rated aircraft not Cessna's and other light VFR aircraft. In the quote you have shown, and in the NG what would you do in cloud at -25 or +5 just out of interest.

[nrcrate 40]

Hi Nick,

 

I thought the posting is refering to the 737NG or any IFR rated aircraft not Cessna's and other light VFR aircraft. In the quote you have shown, and in the NG what would you do in cloud at -25 or +5 just out of interest.

That brochure quote was referenced because it applies to all aircraft, not just small puddle jumpers. In your scenario, I would have anti-ice on as a precaution because those are conditions where icing is most likely (<+10 Celsius and visible moisture) . A wing/engine is a wing/engine- whether large or small and can be affected by ice in the same ways. Better safe than sorry.

[Spin737 102]

Boeing has plenty of guidance on this, guys. Don't go with general GA recommendations. There are plenty of threads on this topic.

 

It doesn't look like he was on final, so a go around isn't appropriate.

 

I also think that there is an idle issue, but this might not be the case at the snapshot taken in the pic. If he's in MCP SPD, then the T/Ls are probably on their way to idle.

[Daveng3 0]

Hi again Nick,

 

The brochure from Aircraft Owners and Pilots Association does not or even imply to be relavant to all aircraft types. I am glad to see A/I is put on even though on the brochure those figures I suggested are not even mentioned. I see also you have introduced which I happen to agree with, a new " most likely limit (<+10 Celsius and visible moisture) " is this also from AOPA as I cannot it see it within the quote net alone the " Below 10K with visible moisture".

[voske 36]

FCOM1 SP.16.9 SP.16.10:

 

Engine Anti-Ice Operation - In-flight Engine anti–ice must be ON during all flight operations when icing conditions exist or are anticipated, except during climb and cruise when the temperature is below -40°C SAT. Engine anti–ice must be ON before, and during descent in all icing conditions, including temperatures below -40°C SAT.

 

CAUTION: Do not use engine anti-ice when TAT is above 10°C

 

There is no definition of icing conditions in the FCOM.

[CaptCraig 226]

Could you please enlarge on this. I had the anti-ice on pretty much all of the flight. Why would this effect the air speed? Or at least the N1? I'm surprised if a decarded setting can make a engine dangously powerfull on decent.

 

 

 

Also please give a more detailed explaination. I don't understand how that can effect the N1?

An idle engine is an idel engine. Or it isn't.

 

I know I'm over the speed, please don't rub it in :P

 

 

 

I wasn't flying at that stage with VNAV. I was using VS and speed hold (MCPS) , as conservatively as possible.

 

Occationally I do get a mesage in the FMC Something like '10 knots above ISA' or something like that. This was higher up up when I was more inclined to use VNAV.

 

haha If you used VNAV you wouldn't have been over speed or low on the decent. That's just what I use, but every pilot is different.

 

Your N1 in the screenshot IS at idle. Idle gets higher when there isn't as much O2 outside so the fans spin faster to push more air through.

[joolsd 10]

There are alot of replys here and it takes som time to read over them, so please bear with me.

 

haha If you used VNAV you wouldn't have been over speed or low on the decent. That's just what I use, but every pilot is different.

 

Your N1 in the screenshot IS at idle. Idle gets higher when there isn't as much O2 outside so the fans spin faster to push more air through.

 

So in a nut shell, what are all you'reaying. The N1 is high,.. due to bleed air situation. But it is not making the aircraft too fast because it is not effecting the EGT.

 

Would continuous ignition effect the decent. I know you are meant to have it on take off and landing, and rain. But it must be easy to forget this item? What if it is on at FL350?

[xxJohnxx 21]

Hi Julian,

 

Continuous ignition probably wouldn't affect your engine thrust. If it is on at FL350 you may want to start using checklists :P

The only thing that will be affected is the lifetime of the ignition system.

 

BTW: The EGT is affected by a higher N1 however more EGT doesn't directly mean more thrust. You don't have more engine power if more bleed air is used, nothing to do with the EGT (directly).

 

Best regards

 

John

[FLEX1978 373]

Julian, EGT is irrelevant regarding descent. The bleed air demand from anti ice requires a higher idle N1, higher idle affects your descent path and your ability to slow the aircraft down. That's pretty much as complicated as it gets when planning your descent.

[joolsd 10]

Hi Julian,

 

Continuous ignition probably wouldn't affect your engine thrust. If it is on at FL350 you may want to start using checklists :P

The only thing that will be affected is the lifetime of the ignition system.

 

BTW: The EGT is affected by a higher N1 however more EGT doesn't directly mean more thrust. You don't have more engine power if more bleed air is used, nothing to do with the EGT (directly).

 

Best regards

 

John

 

Ok that's all good stuff to know. The only reason obviously why this thread lead to the the high N1 is that I thought that it might be causing a increase of power, but I guess that is not the case.

 

But is there anything I could do to slow myself down. I could look at a few things myself. At the top of descent for example, maybe I could slow down even more to 280K. Nice and low, then roler coaster down. Sometimes when ATC is waiting for you and he wants to go to bed. Sometimes you feel obliged not to keep him waiting.

 

Julian, EGT is irrelevant regarding descent. The bleed air demand from anti ice requires a higher idle N1, higher idle affects your descent path and your ability to slow the aircraft down. That's pretty much as complicated as it gets when planning your descent.

 

So it does effect the descent path

Ok cool, I guess just work on the flying and planning. So minimal use of the anti ice is a good thing as this can cause the problem?

[Paul_Smith 92]

Stick to the basics, EGT and anti icing are all just distractions and do not matter until you control what the aircraft does instead of it controling you.

 

As I said, let the computer fly and see what it does. Fly without weather until you can fly well, then when you add weather back in, it will be the only thing you have to manage.

 

If you watch the automatics as the aircraft approachs TOD, you will see the throttles go to idle and the speed drops from cruise to descent speed - while the plane is still level! Only when it is slow enough does it start down. You might see pairs of small green circles on the ND before crossing restrictions where speed is involved, such as at 10,000feet. The aircraft will level off at the first one and slow from current descent speed (usually 280) to restricted speed, (usually 240) and again, only when it is slow enough, will it start down again. The computer is smart enough to work all of this out for you, but only if you give it the correct facts to start with.

[rsvit 16]

Would continuous ignition effect the decent. I know you are meant to have it on take off and landing, and rain. But it must be easy to forget this item? What if it is on at FL350?

 

Don't forget that you have turn on cont ignition while using engine anti-ice. Neither flt or cont ignition affects N1.

And TAI commands EEC to set up approach idle which is higher than minimum flight idle.

[FLEX1978 373]

But he is at low altitude with high O2 density, so N1 should be a little bit lower

 

Lower then what? A huge amount of variables affect idle N1. It always bug's me I read comments like 'I watched this video on youtube and N1, spool up times etc etc are not the same as the sim'

[rsvit 16]

Lower then what? A huge amount of variables affect idle N1. It always bug's me I read comments like 'I watched this video on youtube and N1, spool up times etc etc are not the same as the sim'

 

I'm comparing N1 on high and low altitude now.

 

I agree with you and had closed that topic forever. PMDG has promised us 95% of sameness and we've got it.