Two Questions About Real World Ops

[adamant365 28]

Hello Everyone,I have two questions about how real-world airlines operate in terms of the 737NG series:1. When a V1 speed is calculated, is it supposed to be guaranteed that the aircraft will stop on the runway if an abort is initiated prior to that speed? I always thought so but I want to be sure. For example, at KSNA, the runway is fairly short at 5701'. In a recent flight I made from SNA to DFW, my V1 speed was about 135 knots at max thrust, flaps 10, brakes held until about 75% N1, 10kt headwind. VR was 136 and V2 I think was 142. It seems to me that there would have been no way for the aircraft to stop on the runway if I aborted at say 130 kt. I know the NGX doesn't make V speed calculations based on runway length (or does it??) but in real life, would V1 have been much lower, say, 110 kt to make up for the short runway??2. How much cargo do the real life NG's typically carry on any given sector? Is it generally only baggage or do the major carriers (i.e. AA, DL, WN, etc) add cargo to fill the holds? My assumption always was that cargo is fairly high value and for the money, it's more economical than carrying people since the cargo will never need to eat, drink, use the restroom, or complain about a hot/cold cabin. So, what are realistic values to use for the cargo holds in the NGX when loading the AC??I do appreciate any feedback. I do try to make my flights as lifelike as possible.....

[FLEX1978 373]

1. If you are using a realistic performance calculator then yes. Also a 2 second buffer zone is applied for pilot reaction.Regards

[JRBarrett 3,099]

I'm sure that cargo adds a very significant amount of revenue to any specific flight. Recently we needed a critical part "immediately" at my company, which is to say we needed the part the same day we ordered it - from a warehouse 1500 miles away. Even FedEx priority overnight service would not have been quick enough.The solution was to pay $400 to have the part shipped "counter to counter" on two connecting airline flights, which got it from Wichita to our local airport in the northeastern U.S. within 7 hours.The part came in a shoebox-sized package, and weighed less than 3 pounds, and yet, all by itself, probably generated as much revenue as a single full-sized human passenger riding in the cabin.When I consider how many "small packages" would fit in a typical airliner cargo hold and do the math, ir seems evident that cargo adds quite a bit to the airlines' bottom line. I remember an article here on Avsim many years ago by the late Mel Ott ("Captain Tarmack"), talking about the beginnings of nonstop 747-400 service from Tokyo to JFK in the late 1980's on Northwest Airlines. In those days, the revenue generated by cargo from NRT to JFK typically exceeded the passenger revenue by a substantial margin... so much so, that most flights would have made a profit, even if they had carried no passengers at all.I imagine that financial dynamic is different today, since both FedEx and UPS operate multiple daily trans-pacific freighters between the U.S. and Asia, which wasn't the case in 1989. But I'm pretty sure that even now, most mainline carriers wouldn't survive long if they had to depend solely on passenger revenues.

[Rey 11]

From my time on the ramp working flights, I can't say I remember that many times when our 73s were often filled with cargo, save for the South American flights. There were occasions where there was so much cargo, we'd have to save the entire front or back of the aircraft for freight, if we had the room for all the bags. But I'd have to say the most common types we saw were organ transplants, aircraft parts, human remains, mail, pets, and flowers. Especially during the springtime.

[jeffhunter 0]

the margin should be the distance left after a stop from a rejected takeoff at V1.I ran some quick calculations using TOPCAT 2.70, which, assuming a max TOW at SNI and the current conditions, show that you could stop with about 200 ft remaining. Plenty!!!!!

[JRBarrett 3,099]

From my time on the ramp working flights, I can't say I remember that many times when our 73s were often filled with cargo, save for the South American flights. There were occasions where there was so much cargo, we'd have to save the entire front or back of the aircraft for freight, if we had the room for all the bags. But I'd have to say the most common types we saw were organ transplants, aircraft parts, human remains, mail, pets, and flowers. Especially during the springtime.

Of course airlines are infamous for baggage mixups, even with time-critical items... It was hard enough the year we had to explain to our boss that we were having a difficult time repairing our aircraft with the bouquet of orchids that Gulfstream Aerospace had sent us - but not half as bad as the poor guy who had to explain to his wife why he had sent her a landing gear actuator for Valentine's Day...

[xxJohnxx 21]

For instance Lufthansa Cargo has 18 MD11s. However it is in the top three of the worlds largest Cargo airlines. The reason for that is quiet intresting. Lufthansa Cargo has all rights for the belly loads in Lufthansa's entire fleet. That are about 350 airplanes. Lots of them fly long distances and they probably reach more airports as the MD11s do.

[JakobF 19]

Well to the second question, around summer time there would be around 3-5 tons of luggage and cargo on a NG. And during Winter time its around 1-2 tons, and that from Cph, Denmark. But is varies alot. :-)

[adamant365 28]

Alright, thanks for the great answers! So basically, if calculated correctly, V1 will always leave enough room to stop. That's what I thought or else there'd be no reason to have a "decision speed." Maybe I'll have to invest in TOPCAT to do the calcs in the future.As for the cargo, I'm getting that NG's typically carry some, but not a great deal. When I'm planning my flights in the NGX, I usually pick an arbitrary weight like 60 lbs of cargo per passenger. In my head, that means about 35 lbs of luggage per person and 25 lbs of other revenue cargo per person. So for a standard 150 passenger 738 flight, I would add about 9000 lbs of cargo distributed relatively evenly between the two holds. It sounds to me like I'm getting pretty close in my assumptions.

[mikea76 184]

but not half as bad as the poor guy who had to explain to his wife why he had sent her a landing gear actuator for Valentine's Day...

LOL

[Airbus Commander 563]

Hello Everyone,I have two questions about how real-world airlines operate in terms of the 737NG series:1. When a V1 speed is calculated, is it supposed to be guaranteed that the aircraft will stop on the runway if an abort is initiated prior to that speed? I always thought so but I want to be sure. For example, at KSNA, the runway is fairly short at 5701'. In a recent flight I made from SNA to DFW, my V1 speed was about 135 knots at max thrust, flaps 10, brakes held until about 75% N1, 10kt headwind. VR was 136 and V2 I think was 142. It seems to me that there would have been no way for the aircraft to stop on the runway if I aborted at say 130 kt. I know the NGX doesn't make V speed calculations based on runway length (or does it??) but in real life, would V1 have been much lower, say, 110 kt to make up for the short runway??

For you're answer, V1 is calculated as the go, no go speed. Above you go, below, you must be able to abort with sufficiant room to come to a complete stop on the runway after a 2 second reaction delay. V1 can't be a speed below VMCG or the takeoff is not authorised.

[denver69 0]

One thing to notice in the PMDG is that VR is allways 1 knot above V1. The PMDG does not take conditions like length into account otherwise at strips like KSNA you would see V1 farther below Vr due to the short length. There then becomes a point where you are heavy enough to then be climb limited and then because you cannot make 35 feet over the end of the runway or make the 2nd stage climb slope on one engine if it fails just after V1. The V1 is guaranteed accelerate stop and accelerate go (balanced field) and the PMDG does not know runway length or climb slope. At least I do not think, correct me if I am wrong.

[G550flyer 1,015]

One thing to notice in the PMDG is that VR is allways 1 knot above V1. The PMDG does not take conditions like length into account otherwise at strips like KSNA you would see V1 farther below Vr due to the short length. There then becomes a point where you are heavy enough to then be climb limited and then because you cannot make 35 feet over the end of the runway or make the 2nd stage climb slope on one engine if it fails just after V1. The V1 is guaranteed accelerate stop and accelerate go (balanced field) and the PMDG does not know runway length or climb slope. At least I do not think, correct me if I am wrong.

You are on the track. In the real world the FMC or the performance manual accounts for the runway/airport conditions. Would be nice if this was factored in PMDG. In the Gulfstreams that I fly, there are take-off calculation pages that are part of the perf init section. Here i can add obstacles, climb gradients, runway conditions and configuration to calculate data and v-speeds. As long as my accel stop/go is equal to or less than runway available, i am good. This only ensures that i am not field length limited and i must verify i can clear obstacles and climb gradients. Our fleet also have performance manuals that can be used to calculate the informance in the case of FMS failure of the the performance module. Would be nice if these factors were added to PMDG. Alot of companies will have special engine out procedures created at certain airfields in order to increase takeoff weights when limited by climb gradients and obstacles. These procedures provide an escape route in the event you loss an engine after V1. I just used one these procedures at MMMX due to the high PA and gradients.

[WTE_Pharoah 7]

good topic - mind if I ask a diff question? whats the normal speed/altitude config on approach for the NG? ie. 5000, 180 kts? reason I ask is because the FMC tends to like to put you at 2,000 at 240kts by default with some magical 'deceleration' which doesn't normally happen. I've ended up doing one or two go arounds (and/or fast landings!! :() because I couldn't slow down enough in time. however I've seen (on youtube) a/c being really slow at around 7000-10000 ft.

[scandinavian13 5,192]

In general, if you're doing 250 below about 5000, you'll start getting attention from ATC. Turns at 250 knots are horribly wide, when compared to about 180, and when you're on a busy approach sector, the last thing you need is someone making wide turns. I use 220 passing through 5000. When you're getting close to when you'd expect your vector turn inbound (for the vis or ILS), you should be at around 180ish knots, unless ATC says to keep the speed up.Note on the above: I'm not rated in the 73, and I'm not going to claim I have any official sources on the flight side, but as a guy who trained to be a controller, I'm using what I would like to see as a controller.