Author Topic: Operating above 10.000 feet  (Read 2172 times)

Dimitri Bespalko

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Operating above 10.000 feet
« on: Sat 25 Jul 2015, 14:16 »
Hello dear pilots!


I'm new to JS4100 so I have some questions regarding operating this nice aircraft:


1. I tried to find some performance charts for calculating the correct cruise altitude (altitude/load) but without success. The reason for my search is because I cannot get the altitudes described in FAQ (this forum). For example the flight duration from EDDL to LSZB is about 1:30 so the altitude should be above 20.000 feet (see FAQ) but with 29 pax and about 700-800 lbs cargo on board + anti ice + 98% RPM I cannot get at this height! Also my cruise speed (96 RPM) is about 160 IAS (using AI while cruise).
2. The second important question is about AI: in my sim I use ASN for weather and the thing is when I fly i get 20 times icing conditions... To turn on/off 20 times AI is really strange, when I leave the AI ON then I'm delayed due to lower performance of the aircraft. Is this normal that I have so often Icing Conditions or maybe this is a problem of settings (FSX or ASN)? How the real crew doing in such situations? Leaving the AI ON for the whole flight?
3. When flying in icing conditions my wings getting ice (this is normal:-) ) but I need manualy switch every 2 minutes the Wings AI switch to auto in order to break the ice. The new ice is after 1-2 minutes again there so I need to brake again... So the whole flight I just breaking the ice... Is this normal procedure in this aircraft? No coffee brake at all???


I jumped from B77W to this aircraft because I was looking for short flights. But the thing is that flying the B77W is SO EASY in comparison to this small turboprop aircraft!


Chris Liu

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Re: Operating above 10.000 feet
« Reply #1 on: Sat 25 Jul 2015, 18:46 »
Hi Dimitri, welcome aboard!

1) Getting documentation for the J41 is difficult. Anti-ice has a big performance penalty so it you're struggling to climb with anti-ice on, it's acceptable to use 100% RPM temporarily, normally at 180 KIAS (remember to move the thrust levers forward so you're at the EGT limit again). If the aircraft is still struggling you'll need to step climb until you're clear of ice or lighter (i.e. stay at FL180 for a while), this will happen occasionally. 160 KIAS cruise sounds very slow, you can maintain above 96% RPM until you've reached cruise speed (typically 220-240 KIAS). This is covered in more detail at http://viaintercity.com/forums/bae-jetstream-41-%28bae-js4100%29/advise-on-flight-times/msg1197/#msg1197

Remember: You should adjust the thrust levers before and after adjusting the conditions levers. For climbing, set torque so EGT is near the  red line (VRL).

2) Icing conditions are defined as flight through visible moisture (such as a cloud or rain) between -20'c and +10'c and in those conditions the aircraft should be protected anyway (engine and elevator anti-ice on). If the "ice detect" warning in the cockpit sounds you know to start using the de-icing boots too. Unfortunately, icing in FSX is not linked to visible moisture so the "ice detect" light may come on at other times, then you should use the anti-ice until "ice detect" goes off. I don't use ASN myself so I don't know if it over does icing.

Turboprops suffer from ice more than jets because they use de-icing boots and cruise at altitudes where ice is common (jet aircraft are generally above the icing layer and use heated leading edges all flight). In real life, J41 and Q400 crews turn the anti-ice off once clear of icing conditions because of the performance penalty.

3) You should wait for a few centimetres of ice build up on the wings before activating the de-icing boots. The Q400 uses a timer for this, but in the J41 each cycle is manually commanded. Once every 4-5 minutes is normally enough.

Welcome to real flying!  ;D The J41 and Q400 are challenging aircraft that have to be flown the entire flight and require skilled pilots. Although I usually find time to get a cup of tea in the cruise.
« Last Edit: Sat 25 Jul 2015, 18:49 by Chris Liu »