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Some questions I was asked....
3 replies to this topic
Posted 19 August 2010 - 02:13 AM
Captains-A few nights ago, I made the mistake of telling Paul that I was completely caught up on my (small) part of the support queue. Since he was worried that I might get bored since I only have the NGX on my plate for a few weeks... He forwarded an unusual support request that had some questions about the JS4100.Normally, we have to decline to answer such requests personally- as it simply isn't possible to teach someone to fly a complex airplane by email. This one struck my fancy, however- so I gave the answers a shot.After sending the reply- I thought some of you might wonder about the same things- so I figured I would re-post the discussion here for your enjoyment.I'd also like to thank Mikael for his questions- he approached the topics in a way that made it hard not to enjoy answering them....Thread follows:=================Mikael-Paul forwarded your ticket to me for handling, because he thought that a few thousand hours PIC time in the JS4100 might qualify me to answer your questions.(We shall see if he was mistaken!)[High speed situations in an approach]When I was approcching Insbruck(LOWI) which is a quite challenging approach the tower complained several times during my approach down the valley that I should "KEEP HIGH SPEED!!!" My approach speed was 115 IAS and VREF 100IAS. I told him when I had landed that he should know that not all airplanes are jet aircrafts since his complaining was quite annoying. Then he said that in real life pilots use to keep up speed until AB ndb before lowering the gears and extending flaps. I am aware that on most larger aiports atc wants you to keep 160IAS until OM but it's not thateasy to get the plane down to vref in around 4 miles considering passenger comfort and also remaining within accepted glide profile. I was especially careful when descending towards Innsbruck LOWI with those high mountains surrounding the airport and lowered the gears and reduced to app speed 115 IAS before catching the glide to be able to stay on the glide and still have full control. I guess the atc wanted me to keep at least 160 down the glide or something but I have tried that once and then it was realy hard to reduce the speed and the same time performing a stabalized approach. How does real life JS41 pilots handle these "high speed" situations in an approach. On VATSIM I'm often "forced" to fly to or from quite big and busy airports where those speed requirements exists from atc if I want to have atc present since the bigger airports are more often open.In the operational environment, I flew the JS4100 in the northeastern USA, which is some of the worlds most congested airspace. We flew the airplane out of a hub at Washington DC's international airport, and we flew to all the major international and domestic hubs on the US east coast, as well as small towns and cities away from the big jets.Our standard approach process involved flying the airplane at ATC designated speeds and altitudes until we were being vectored for the final approach. At this point we would slow the airplane to approximately 170 knots, keeping the airplane clean. Generally speaking, in the USA, the ATC folks will set you up about 3,000' AGL in level flight to intercept the final approach course and glide path. This being the case, we would maintain anywhere from 210-170 KIAS until we saw the glideslope come alive. At this point we would pull the power to flight idle, and being configuring so that we would intercept the glideslope at Flaps 20/Gear Down. We would then begin slowing gradually to 145 knots for the final flap configuration for landing.If you look at the weight/speed cards in the cockpit, you will notice that Vref is generally around 120 KIAS for a reasonably loaded J41. We would plan to be at Vref at 500' AGL on a VMC approach, or at 1000' above DH on an IMC approach.So- the conclusion is this: You get used to the slow rate at which the J41 slows down- and for IMC approaches- you plan ahead and you fly at Vref from 1000' above DH until touchdown. No professional ATC controller would complain about this- as they understand the procedure just as well as we do.(While I was Chief Pilot at our airline, I had an ATC yell at me on the frequency for refusing her request to maintain 190 knots to the final approach fix. That was a mistake she only made once in her short career, I believe.)[RNAV TMA Procedures]Then I have also some thoughts about the RNAV procedures at bigger airports not using conventional SID and STARS. I assume that the equipment present on the JS41 is aproved for B-RNAV TMA procedures only and not P-RNAV TMA procedures? Folowing a SID out of LOWW for example. They do not state if it is a P-RNAV requirement or not but I guess I will be below the MSA at the first waypoints of the SID so then it is not suffient with a B-RNAV only equipment? Following a STAR inbound LOWW though you'll never be bellow MSA between any points of the STAR(transition) so I'm certified to fly that STAR(transition) then? I think it's a litle bit confusing sometimes to know when I "can" follow a SID STAR or not in order to simulate the rel life procedures which I think is fun.I believe your interpretation here to be correct. At the airline we had it easy: If the procedure was in our company database in the FMS- then we could use it. :-)[Engine Anti-Ice vs. speed]Then I have a thought about the engine anti-ice. When I get the "ice detect" message, does that mean that it is time for me to turn on the engine anti-ice or is it to late cause the sensor has picked up a lot of icing? Is it normal for me as a pilot to turn on and of the engine anti-ice several times during a one hour flight at FL150-FL160. Sometimes I am not able to cruise faster than 240TAS when having engine-anti ice turned on and without it I cruise at 300TAS without any problems. Sometimes the engine "ice detect" dissapears and I'll get some time to speed it up to 300TAS before it comes back again. Am I doing this right? I'm just quirious if this is the life as a JS41 pilot.Yes- you are doing this correctly! The ice detector is EXTREMELY sensitive- to the point of being an annoyance to the pilots. It detects ice long before visible traces appear on the airplane- which is the reason why it is installed. Generally speaking, we would turn on the EAI before entering visible moisture (clouds or rain or fog, etc) if the temperature was between -10C and 10C. This was a precaution, but it gave us protection that we would not fly into severe icing with the airplane unprotected.EAI is a HUGE performance killer on this airplane. In summer it was not uncommon for us to limit our climb below the freezing level in order to improve KTAS. Climbs to high altitude with the EAI active were slow at worst... and sometimes impossible. Fortunately- overall performance of the airplane improved dramatically in the cold of winter- so EAI performance drain wasn't as significant. In summer however- EAI was something to be mindful of...[Wing Anti-Ice]Regarding the wing anti-icing I have to press the "auto cycle" button all the time if I want the wings clear of ice during flight,is this really correct modeled? I have tried long cycles when below -5C but no difference I think.We almost always used the AUTO cycle. It provides you with the best overall ice shedding. We never really used any other setting unless the AUTO setting was deferred by maintenance. It is correctly modeled that you must activate the ice shedding. This was done intentionally- as the inflation of the boots changes the lift characteristics of the wing slightly- so you never wanted the airplane engaged in such activity unless the crew called for it. (Think: final approach in a snowstorm!)In all seriousness- the difference between the various deice/anti-ice modes on the airplane were so small that we couldn't really tell the difference between them. The engineers tell us that they are all different- but it was never noticeable to us.Thanks for your time helping me to straighten things out a bit.I really enjoy flying the JS41 and it really takes some practise to master it and at the same time fly to large busy airports online at VATSIM.But it really is fun and the product is amazing!Glad you like her! She is one of the favorite airplanes I have ever flown- and I think our simulation captures her nuances (good and bad) very well!Robert S. RandazzoPMDG
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Posted 25 August 2010 - 09:17 AM
Thanks for posting this information to all of us! Very interesting reading, especially coming from someone who has been flying the plane for real.One thing got me thinking... In the J41 there is no VNAV or such, so you would have to keep a look on your vertical profile by yourself anyway. Not being able to meet the MSA at some waypoints should therefore be a limitation of the performance of the airplane, rather than the equipment, right (that explains why it's more critical for SID than STAR)? As I understood, in real life, the procedures that the airplane can not fly are completely excluded from the FMC? And if this is the case, the ATC should just give the headings/speed/altitudes during departure and you ignore the SID completely? Should the ATC already know that the procedure can't be flown with a specific airplane, or do you have to report it first?