rgamurot

The best way to see the effects is when you're climbing. Look at the MD11 for example. Your TAS (the speed the aircraft is moving through the air) is something like 490kts. But you'll notice that your ASI only indicates less than 300kts above FL350. This is because the air pressure (and density) is much lower than at sea level. The pitot tube measures airspeed by comparing the static pressure to the pressure generated by air being forced into the pitot system. With less pressure (and density), there is less stuff to build up pressure in the tube itself.

Sorry for the confusion. 21,000lb figure I mentioned was just how much force would be acting on the reverser system, not how much thrust you'd actually get if your could throttle the engines to full in reverse. But even 8,700lbs is a pretty good amount of reverse thrust. Keep in mind that the reversers in general don't provide very much stopping power at all. The spoilers actually do a better job of slowing the aircraft than the reversers. This is why you never see the effects of the reversers factored on landing performance charts.

It's the temperature at the airport. I will be honest though, I don't know where on the airfield the wx instruments are located. And as far as air density, generally yes, in the winter it's denser and during the summer it's less. But keep in mind that pressure and temperature is what determines density. If it's an abnormally hot winter day with say A29.67, your are going to have air that is less dense. Opposite if it's a cold summer day with a high altimeter setting.And yes, lift is also one of the additional factors that is affected by density altitude. But your speed indicated on your instruments during approach will remain the same for the most part. The determining factor there is weight, not so much density altitude. The reason is that if the density altitude is higher (this means higher altitude, not higher density), there is less air to ram into the pitot system. Less air means a smaller indication. To adjust, you fly faster so you indicate say a normal approach speed of 70KIAS and so now your wings still have 70kts worth of airspeed flowing over it. This is also done automatically since usually the only speed indication used during approach is your ASI. Looking at that your won't notice if you're flying faster or slower than normal. So 70KIAS at high density altitude is still the same as 70KIAS at low density altitude. It's your ground speed that will be different.

Here in Honolulu it can get to just above 32C sometimes. This does lead to longer takeoff runs and slightly slower cruising speeds. Regarding thrust, it's not that we need to use less. We actually need to use more to get the same performance but the engine is incapable of producing that much power. The problem (turbine or piston) is that with hotter and even humid conditions, the air density is less. This means that it has less air compared to denser air conditions to work with.We call this density altitude, which really actually takes more temperature and air pressure into account. Humidity does have an effect but it's small enough where its not too much of a concern. Basically, density altitude is the altitude the aircraft 'thinks' it's at. For example, say it's standard pressure (29.92in or 1013mb) but it's 32C degrees out and your at HNL (13ft elevation but we'll keep it simple and use 0ft). Your altimeter will read 0 but your aircraft will perform as if it were at about 1900 ft. Thus although your true altitude is 0, your density altitude is 1900ft. As I'm typing this, the conditions at HNL are 29 degrees and A3001. Given that, the aircraft will behave as if it were at 1500ft while it is on the ground.Conversely in the winter here, the temperature sometimes gets to a down right icy 18 degrees centigrade (sorry, couldn't help it). Assuming that temperature but still A3001, the aircraft will perform as if it were at just 200ft. The colder it gets or the higher the altimeter setting, the better the performance is. The reason once again is how much air particles are in a given volume of air. It's almost like breathing, the less air there is, the worse your perform.

I don't know very much about the TU154 but no other aircraft mentioned in this thread allowed the throttles to be moved forward while the reversers are engaged. Even though with a majority of aircraft only the bypass air is redirected, keep in mind that at low altitude, that's 80% of the thrust coming from the engine. So in the case of the NG assuming 27000 lbs of thrust at full throttle, that means the reverser system would have to withstand over 21000lbs of force trying to rip it off. With that much reverse thrust, the aircraft would just about be able to go over 100kts backwards...assuming the turbine section could handle all the air being forced up the tail pipe.

After the 3 Hawaiian leased from Qantas, I just found out yesterday 3 additional 71's were leased. I don't know if it was Qantas again or another owner.

To my knowledge there isn't a single aircraft that allows this to occur. The amount of reverse thrust is controlled by how far you pull the reverse levers past reverse idle in every aircraft capable of reverse I know of.Also in response to the first question (how do they work), for the NG specifically, see my post in the MD-11 forum HERE. The engines may be different but the operation principle is identical.

I want to say they have done this at least with the MD-11. Since it's such a large aircraft it is difficult to tell and to be honest I never really looked. However, whenever I start a flight, I always start with about 7 tonnes of fuel on board and use the refueling option. From the inside, I do notice the MD11 is lower when fueling is complete. It would probably be much easier to see with something smaller like the NGX.

The magnetic compass is worse. It's behind, yes, BEHIND the FO's right shoulder. They have mirrors on the glareshield that fold up and are adjustable to view it. I've heard it's a nightmare in turbulence.

Well I know Hawaiian took a few off their hands a few years back. I think they took a total of 4 and ferried them up after Aloha went under to meet demand. I've been saying it for a while that I would love a 717 since it is practically the flagship of Hawaiian airlines. (Although those new A330's are getting good reviews. I still wish they went with 777's.) I've always wanted a good rendition to run interisland routes on.Very nice picture by the way. What airline is that? And when was it taken because that flight deck looks way to clean to be recent.

Well technically the data TOPCAT has should be compatible with any 737 addon since you can adjust the weight of the empty aircraft yourself. For the most part this is what is done in real life. It's completely impractical to develop performance charts for each individual aircraft that rolls out of the factory since ideally they should all perform the same. Sure this isn't true and even the performance degrades over time but to factor that in also would be a nightmare. Its' far easier to make a master list of performance factors at a given weight with given atmospheric conditions that is basically close enough to the performance of an average aircraft. If not, its a brand new aircraft flown by the best pilot and you factor in your own buffer. So basically at the end of the day, you enter the weights for the aircraft (ex. N5329L), then use tables, graphs, whatever for that specific model (ex. B738), and finally adjust for things like runway conditions to obtain your performance figures.

Just as a note, the current release of TOPCAT already comes with -700 and -800 profiles. They could possibly be refined and the -600 and -900 added in, but there are already profiles there.

I never said you didn't need a bit of extra thrust to start moving, just that I almost never need more than idle thrust while taxiing. Most of the time idle is too much and we need the brakes to keep the speed under control. But this is because the route from our ramp to the runways we usually use almost always gives us tailwinds on the ground.

Every aircraft I've flow except one will gladly taxi at idle power. Some even need a dab of brakes to keep the speed under control which isn't easy. It's tempting to ride the brakes but then you will risk them overheating. The only aircraft that needed more than idle thrust to keep going was an old 1972 C182N.Remember that especially jet engines are still producing a huge amount of thrust even at idle. Once a nice little challenger at idle maybe 100 ft. in front of me tried to flip the C172 I was getting ready to fly. A friend of mine did get flipped behind an MD-11 starting up (Thank you FDX). There was about 200ft. between the engine and the taxiway. Ah, the joy's of flying GA at a Class B field.

Yes but the final authority over the aircraft in this case would've been the ground crew towing the aircraft since they should've seen everything around them. Ground can give a clearance but it's only their responsibility to make sure you don't hit ground crew or other aircraft or cause some sort of incursion. Not hit a stationary object such as a very large building.

This is great! I love seeing how the different systems work in depth. I didn't even know the compressor for the bleed system was separate from the engine. I am the sort of person who just stares at all the technical drawings in all of my PIM's. I just find it all fascinating. Sometimes I think I should've become an aircraft mechanic instead of a pilot...sometimes... :(

I was watching ITVVs 737 program and the captain mentioned that the left trim wheel was made by a completely different company than who makes the right side trim wheel. Does anyone know why the same company couldn't just make both and if the NG's have the same quirk?

I guess it really just depends on the company or even how long they'll be on the ground. The interisland flights here (mainly 717's and CRJ's) never use GPU's. Some other airlines won't use GPU's if their stopover is less than 90 minutes. Some will no matter how long their stay is. But I've been told a lot of the time they will use the APU because it's actually cheaper than using ground air.

For some reason, instead of thinking this person needs help, i'm actually a bit jealous.

I see. Thanks again for all the information David!

It certainly does! Thanks. Do you know of any other airlines that may depart with the APU off and then start it before entering the Extended Range Point? And do you consider extra fuel compared to an overland flight of the same length?

As robert said, yes. And Ryan had actually explained back in January how it was modeled...sort of

Sometimes they don't even have to let the brakes cool. Here at HNL, most of the RTO's are ordered by tower just as the aircraft starts rolling. Only once have I seen an RTO here where the aircraft was actually going a decent speed and it was a C208.

I believe it was about 3 years ago when I actually met Mimi Tompkins. It was a Fly-in here at HNL. The only catch is I didn't know who it was until afterwards since she just introduced herself as Mimi. There was another report I saw that speculated that the chief flight attendant, the only casualty of the flight, might have actually been the cause of the massive failure (not on purpose). The report speculated that when the one section failed, Ms. Lansing was sucked toward the hole. When she 'plugged' it, and the air suddenly stopped rushing out and repressurized the aircraft causing the rest of the area to blowout.On a lighter note and back on topic, you people really need a life!:(

Thanks for the clarification. I'm guessing the reduced N1 and fuel burn is due to the altitude. I'm sure the real world operators fuel calculators automatically take the APU use into account but for FS, does anyone know roughly how much extra fuel I should plan for? For example maybe 200lb per hour. Then again, if the fuel burn is that low, do I even need to worry about extra fuel for the APU?