Al Czervik

coming from a guy that loves the 737. Questionable judgement at best. 🤣

aa73

Thats funny, and even funnier because I flew with him when he was on the 737 as well 🤣

Sliceback

Been out of the loop for a couple of weeks. It's been 13 yrs since I've been on the 737-800 but I think the (fairly accurate) rule of thumb was 160K = FL360 OPT ALT. OPT to MAX ALT typically 1700-1800'. Every 1000 lbs moves OPT ALT 150 lbs. TOC fuel burn in typically 8000 (?) lbs. So the heaviest you're getting to altitude is 165K? 5000 lbs heavy x 150 ft = reduction in OPT ALT of 750 feet. So perhaps 35,200' for a 174,000 lbs takeoff weight.

Again it's been 13 years and I'm not looking at my cheat sheet so I'm going off of memory.

Airbus is different formula. Different charts, etc. so I ended up using a different rule of thumb. Keep in mind when discussing OPT ALT on Airbus's I'm using the REAL OPT ALT, as Boeing uses, and not the wind adjusted altitude that Airbus calls 'OPT ALT' but Boeing calls 'Recommended ALT'.

Airbus rule of thumb is 510 (520?) minus aircraft weight in tens of thousands. 170K bird? 510-170 = FL340 OPT ALT.

The wings aren't getting bigger on the 737-9 and -10 so the rule of thumb should be the same. A321XLR is 220,000 lbs. So coast out of Ireland might be 205,000 lbs, or less? 510-205 = 30,500 OPT ALT (Boeing OPT, not Airbus OPT). If 520 is a bigger base line it would be 520-205 = 31,500'. So FL320 might be a reasonable SWAG for the lowest alititude the wing might get to with a max takeoff weight out of Ireland to the U.S.???

Every airplane has this data point. 777-300 gains 37' per 1000 lbs of weight reduction? 777-200 is 40'. 787 is 47(48). Use 50', it's close enough. 767-300 is 70'/1000 lbs reduction. 757 is 100 per 1000 lbs. N/b's all seem to be around 150' per 1000 lbs of weight reduction.

The nice part is you instantly know what your OPT ALT is once you see the takeoff weight. If you're not at OPT ALT it's worth finding out why? MEL? Ride report? Winds? ATC restrictions? The TOC fuel burn is typically the same. Upper single digit thousands for n/b's and low teens for w/b aircraft. Subtract that for your takeoff weight and using the rule of thumb you know you're TOC OPT ALT. Knowing your climb fuel burn and it's impact on OPT/MAX ALT means you can look at the OPT/MAX ALT on the ground and figure out what your TOC OPT/MAX ALT would be. It's typically 900' (??) higher in a n/b from takeoff to TOC weight.

It also helps to understand how your company's flight planning system works. At AA cruise altitude could not = MAX ALT. But it WOULD put you at the top of the performance chart if MAX ALT was 100 greater than cruise altitude.

It's one of the first things I'd do when the flight plan came out - what's my TOC OPT ALT? Knowing provides MAX ALT info - an additional 1700-3800' depending upon a/c type. Next is to check the planned altitude. It's just a computer spitting out a number of it would happily put the aircraft 100' below MAX ALT. Unless you check you might not realize it.

Sliceback

The reference to the 80's was obviously lost on some...it's not like that today. But hub flying has been hub flying since the 1970's. East coast hub flying, especially the north/south flying, is the worst. Short legs = more legs = inefficiency (flight time vs on duty time vs time away from home). This hasn't changed since they figured out the earth was round. That's why DFW hub flying was generally considered better flying for east coast guys than ORD hub flying...DFW added more time to and from the NE. Over a month it added up. CLT is the exact opposite.

Sliceback

Geez, why didn't someone tell me a bro love fest was starting?? ;-)

But he's right about my knowledge fading AND my n/b flying has been limited to a handfull of years over the last 20 years. But a lot of this is basic stuff and it's laughable when guys complain, especially new/young guys(!!), complain about what the job is. Basic research would have told you.

I, and many, stumbled into dumb luck by not having to do a lot of N/S east coast hub flying. I was thinking of moving to RDU if it grew into a CLT/ATL/DFW type hub for AA back in the 1990's. It didn't so I didn't move. Dodged a bullet there as many guys had to commute, or move, as the RDU hub went TTFN.

You want to do a ton of legs everyday? Go to SW. Or bid east coast N/S flying with short legs. That's GREAT for a new guy to get up to speed on. But those trips go junior for a reason as guys get more seniority.

J3nkums

Not true. Im on the 777 based in DFW and have alot more than just LHR. But please continue.

cornerpocket

Some great info here, Slice

Sliceback

You're welcome. Every airplane has a weight / OPT ALT combination that's easy to remember. I'd have to go check but I think the 777-200 was 510,000 lbs = FL370???? 777-300 was 560,000 = FL FL350??? 787 was 460,000 = FL 380???? A 1000 lbs weight change moved the 777-300 by 37', the 777-200 by 43', and the 787-8 by 47'. I think those are close. It's easy enough to figure out - enter different ZFW weights to get different aircraft weights and verify the change in OPT ALT's.

It's nice for doing trans-Atlantic or other flying that has specific entry and exit gates after which in can be hard to change altitude in non-radar airspace. Take your takeoff gross weight, figure out the fuel burn to coast out, and apply the correct factor (feet per 1000 lbs change) and you can know you're estimated TOC cruise altitude, ideal coast out altitude, and max coast out altitude before you even leave the hotel. You can also figure out your expected cruise altitude at the end of the non-radar/oceanic point. Or when climbing (assuming weight is the primary factor) would be worthwhile.

You can also use it to estimate the aircraft's OPT/MAX ALT combination at any point along the route of flight. Weather x hours ahead? Do the math....and you'll know the aircraft's OPT/MAX hours beforehand. It ALSO allows you to '**** block' (a Deep South term about getting higher than desired sooner) to claim squatter's rights for that altitude before reaching the ITCZ.

Back when aa73 were slumming together on the 737 I told the FO my altitude requests for the WATRS southbound to SJU. "We're too heavy for that with the weather on the route." Refused to ask ATC for the altitude. I asked...up we go.* Next leg was SJU-BOS, again had to make altitude call for non-radar airspace and dealing with the weather, and knowing our weight which really meant altitude (OPT/MAX) capability mattered. Day 2 was BOS-SJU. Again dealing with enroute TSTM's in non radar airspace. FO wasn't pushing back on my altitude calls. Leg 4 was SJU-BWI...again dealing with weather on the Red (?) routes. Going non-radar FO says "I owe you an apology about yesterday." 'Nah, we're good.' "No. I owe you an apology. I didn't realize you knew the numbers that well and did that every flight. I was wrong. But I've been with enough guys who DON'T do that analysis and have sat through too many dumb decisions. I thought you were doing that again. Turns out you know what our numbers would be at the weather. I was wrong."

N/b's high, like the A321 and 737NG's, have small windows between low and high speed buffet. 777-300 is similar. 777-200 and 787's are beasts - 3000-4000' between OPT and MAX. Much easier to go 1000-1500' above OPT ALT. That's a TOUGH call with weather in a non radar environment (if you can't hang in at altitude....)

* - I've seen some say "if the FO's not happy..." and let the lowest common denominator make the decision. I've flown with FO's who didn't like going above FL310, or within 1000-2000 BELOW OPT ALT. Listen to their input. If you know your ****, and their concern has no merit, be a Captain and figure out what you think is the best decision. I have to laugh about guys that fly low, and fast, and then complain about arrival fuel. Had that on the tracks and a UA 787 kept asking for higher. Air Canada above them couldn't climb. "Well we might have to land short if we don't get higher." After about the 3rd whining call the reply on 123.45 by an unknown flight was awesome - "you're 4000' (6000'?) feet low on the tracks, at .87, and you can't figure out how to make the plane more efficient?!?!"

Sliceback

To figure out the real OPT ALT, per Boeing's terminology, look at the OPT/Recommended MAX before entering any winds into the FMC. IDK if the numbers change with the bigger engines but it should be close to 510 (520?) minus (aircraft weight in 10,000's lbs) = OPT ALT. Eg 160,000 a/c - 510 - 160 = 360. Another AIrubs issue is the FMC only shows nearest 500' while the Boeing displays to the nearest 100'.

ClncClarence

Not sure what you are referring to. The Prog page on the ‘bus shows OPT and REC MAX in 100 foot increments.