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enrico68

Quick question on PMDG J4100 correct climb speed

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Hello PMDG J4100 fans, I have the following question: according to the manuals, the climb speed for the PMDG J4100 is 170 kts, and no less. Problem is, when passing say 16/18000 ft, and flying into thinner air, if I keep IAS 170 knots, the J4100 climbs ever slower, until it barely keeps 100/200 fpm climb, and at that rate if you want to climb to say 22/23,000 ft it would take forever. Only solution I use is to allow a lower climb speed, like 160 kt or 150 kt, this way getting a reasonable climb gradient. I know this is not a big deal, but I would like to understand if my procedure is correct, or if there is anything wrong I am doing . Looking forward to any suggestion, many thanks in advance,

 

Enrico :smile:

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Sounds like you are cruising too high for your weight, don't expect to get above FL200 unless you are light - it will be even less if you're in icing conditions!

I normally climb at 170-180 kias with 98.6% rpm myself, if the climb rate drops below 600/700 fpm then I increase to 100% (MCT) until I reach ToC (this is permissible and what J41 pilots do in reality). Of course, you can reduce IAS too, but if you have to reduce below 170 kias are probably asking too much of the aircraft and should elect to cruise at a lower level.

As a side note make sure you're not overloading the fuel for your sectors, if you land with more than about 1200 lbs fuel on board, you're over filling the aircraft.

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Only solution I use is to allow a lower climb speed, like 160 kt or 150 kt, this way getting a reasonable climb gradient.

 

There's another solution:

Use a lower altitude.  As Chris mentioned, you're probably too heavy for the altitudes you're going for.  This isn't a jet, and can't be expected to perform like one.

 

From the ATC side, there's no harm in requesting another altitude.  If you file something and it turns out that you can't make it, just let them know you're going to cruise at a lower level.  A few keystrokes and you're all set.

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Hi Chris, so, it seems it is a matter of weight. You are most likely right, I did not factor that into the equation, my bad...I'll try with lighter setups to see how the J4100 behaves, thanks a lot for pointing that out. Tonight is test time..lol...thank you so much,

 

Enrico :wink:


There's another solution:

Use a lower altitude.  As Chris mentioned, you're probably too heavy for the altitudes you're going for.  This isn't a jet, and can't be expected to perform like one.

 

From the ATC side, there's no harm in requesting another altitude.  If you file something and it turns out that you can't make it, just let them know you're going to cruise at a lower level.  A few keystrokes and you're all set.

 

Hello Scandinavian, you are pretty much confirming what Chris just said. It's just that the operating ceiling for the J4100, if I am not mistaken, should be around 25,000 ft, and I was doing some tests to see how it behaves at that altitude, I was probably trying to get up there too heavy for those engines. Lesson learned! Thank you,

 

Enrico

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It's just that the operating ceiling for the J4100, if I am not mistaken, should be around 25,000 ft, and I was doing some tests to see how it behaves at that altitude, I was probably trying to get up there too heavy for those engines. Lesson learned!

 

Right.  Remember, though, that service ceiling does not mean that it is capable at max gross weight (or even average passenger loads).  It's just like ranges: you're not going to hit quoted max range numbers with a full aircraft.

 

No harm in the question though.  It's a common misconception - there are a bunch of similar questions over in the NGX subforum, too.

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No harm to reduce the climb speed a bit. In fact, on it's predecessor, the JS31/32, it's standard procedure. Regular climb speed there is 160kts until 15000ft, after that reduce with 3kts for every 1000ft. Just make sure you stay on the right side of the power curve

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Its a limitation of the aircraft. You cannot climb at less than 170 KIAS unless you are single engine. Ch 3 Pg 12 of the AOM.

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In my manual it makes the point that you can climb at M0.35 which you hit sometime after 15000 PAlt. So I bring the IAS down when it rises above M0.352, though at higher altitudes you get near the stall - when Fsx wind speed changes rapidly (eg a sudden headwind component  to tailwind) this can happen.

Incidentally, in standard met conditions in temperate climes I can get to max altitude when fully laden, buit it takes time and distance (150 nm) - you need to settle at 15 or 16000 ft & see if it can maintain M0.45 (which I find is a realistic figure). This equates to 276 TAS @ std met conditions, (M=39 root Temp K degrees).

If your speed settles higher or rises @ 96.1% rpm & max save temp, go upt 2000 ft & see how that goes. you can use higher rpms of course, but being Scottish I believe in fuel efficiency!

In hotter/tropical conditions sometimes 16000 ft is the best you can get with those parameters. FS9 & FSX just make the temp @ alt 2 degs cooler per 1000 ft than the surface temp! This is not necassrily the case in the real world!


I forgot to say, 276 TAS/M0.45 is @ 20,000 in std conditions!

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