A320 flex to temp

Nice video.

Being in default neo Im limited, but watching your video I can see you have auto breaks on max at takeoff, never enabled them for takeoff before.

Also you go into open climb, I normally just leave it in managed.

Ohh yeahā€¦ I forgot to read the Xbox tag in the topic.

The MAX autobrake is set that way because itā€™s the proper procedure for takeoff. In case of a rejected takeoff (issues or hazard on the runway), pulling back the throttle to full reverse will have the aircraft automatically engage the RTO mode. Which means it will apply full maximum braking automatically while deploying the spoilers and engine full reverse. Without the Autobrake to MAX, youā€™re losing the extra stopping power from the wheels to stop the aircraft before you overshoot the runway.

I usually do this as well, but since Iā€™m using the FBW A32NX, Managed climb will engage the VNAV function in the aircraft (the default A320 doesnā€™t have this feature). So if I leave it in managed climb, the climb performance will follow a set profile and will take the SID altitude constraints into account (ie. it will level off at the set altitude constraints at every waypoint in the SID before it can continue climbing). Since the default ATC doesnā€™t take that into account, they usually get upset and keep telling me to expedite my climb while clearly thereā€™s an altitude constraint on the next waypoint. So I switch to Open climb to disengage the VNAV function and disregard any altitude constraints, so the ATC is happy.

The default A320 have both Managed/Open climb behave the same way, which is not what it should be. The FBW A32NX on PC has fixed this function, and itā€™s now behaving the way it should. But since Iā€™m still using the same default ATC, I have to make my aircraft behaves similar to the default A320, so Open Climb for me.

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Good to know.

I also noticed you set altitude to your cruise of FL39, I normally set it to whatever ATC tells me at the gate, for example 6000ft, I suppose itā€™s easier to just set my cruise altitude straight away?

Well, it dependsā€¦ Iā€™m just personally too lazy to follow ATC simply because as soon as you reach the altitude the ATC will assign you another one until you reach your cruising altitude. So the aircraft goes through this porpoising cycle of leveling off, then climb, then leveling off again, then climb, etcā€¦

I just set it straight to the cruising altitude, and let it climb all the way through, and ATC will just keeps on giving you a new altitude assignment as soon as you reach it and since I donā€™t level off, I continue climbing.

The downside to that is, it can be easy to ā€œovershootā€. This usually happens if you are passing the altitude that the ATC assigns you, but the ATC is busy communicating with another aircraft traffic. By the time theyā€™re free and see your altitude, you are ā€œaboveā€ the assigned altitude, and will tell you to descend to the assigned altitude. So you have to level off, descend, level off again, and once you do reach it they will assign you a higher one anyway, and you have to climb again. This part is annoying, but fingers crossed, most of the times I rarely get this scenario.

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Fair enough. Obviously the Airbus works differently to Boeing then.

The point stands that to have a great experience in the 320NX that calculator spits out something that works, so Iā€™d still recommend it.

Sure, no arguments here. To be frank unless someone is going to be testing whether they can still stop close to v1 without over running (and that would of course make a huge assumption that stopping distances are remotely accurate in the sim) any middling flex setting such as 50-60 will likely suffice in most circumstances. Given however itā€™s a sim and one doesnā€™t worry about engine life, TOGA all the way if you ask me :rofl:

Anyhoo - Just thought it would be helpful to add the info about the TREF since the discussion was being had anywayā€¦

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Hell yeah! :sunglasses:

Sure. An aerospace engineer with specific expertise in airplane performance and airplane certification.

First of all, a flex (Airbus terminology) or assumed temperature (Boeing terminology) takeoff is a reduced thrust takeoff, not a de-rated takeoff. You can use an assumed temperature with a de-rate, but an assumed temperature is not a de-rate by itself.

While you may have used 25 degrees as an assumed temperature or flex temperature at some point, it would not be a valid flex or assumed temperature at KSEA (airport elevation of ~400 feet). 25 degrees is ISA+11 C at KSEA. What engines are on the widebody you fly that have a flat rate temp for takeoff thrust lower than ISA + 11 C?

Ok, fair enough, though there is no regulatory prohibition of such use. It was only being used as one example of how poor this calculator is. Not only will it return ludicrous results for such an example, it does not provide an option for forcing a TOGA thrust calculation. Run it with packs on, and you get a whopping 53 C flex for 60,000 kg, again well under what should be near a 70 C flex condition.

And thatā€™s only the Flex temp portion of the calculator. As I noted in my initial comment, the speeds are just as bad, if not worse, with differences of 10-15 knots or more between VR and V2.

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So on update on the overspeed issue, I tried a few takeoffs today from Heathrow, all I did different was add more payload to the aircraft and used flex to temp of 69.

Perhaps it was the weight after all or I was just doing something wrong on takeoff, perhaps not rotating enough,

Weā€™re in danger of going off-piste here butā€¦

I never said Iā€™d used 25 degrees at Seattle, something highly unlikely with a 10hr flight in front of me. You saidā€¦

I was pointing out that that is incorrect.

Secondly, whilst youā€™re absolutely correct (although a bit pedantic if I may say) that there is the ā€˜de-rateā€™ and ā€˜assumed temperatureā€™ methods, the reality is we often talk of it as a ā€˜double derateā€™. Weā€™re talking on a flightsim forum, not in the classroom.

Thirdly, as I said to ZeeFlyBoy, Airbus must work very differently to Boeing because Iā€™ve never seen an assumed temperature on a Boeing of more than 50 degrees. On the 787 (my current type) they generally vary between ~25 to ~45 and are most commonly in the 30ā€™s. As Iā€™ve never flown an Airbus Iā€™ll have to believe what you say.

Yes, Iā€™ll admit to being pedantic (or even worse, a bit ā– ā– ā– ā– ) about using the correct terminology for reduced and de-rated thrust. But I think you were also being pedantic about the 25 C comment where I was obviously (but maybe obvious only to me??) that I was referring to the KSEA result from the takeoff performance calculator. And it wouldnā€™t matter whether you had a 30-minute or 10 hour flight ahead of you. 25 C would not be a valid Flex temp from KSEA or any other airport near sea level.

As far as the maximum assumed temperature goes, the 737-600 with CFM56-7B22 engines has maximum assumed temperatures from approx 40 to 70 depending on the pressure altitude and OAT. The maximum assumed temperature is generally limited by the requirement that the resulting thrust is no more than 25% of the normal takeoff thrust and no lower than the climb thrust at the same conditions. It is true that Airbus have managed to sort of ā€œget aroundā€ the climb thrust limitation by temporarily reducing climb thrust when the thrust levers are moved from the FLEX detent to the CLB detent.

Interesting. I flew the classic (3/4/5) and Iā€™ve regularly seen assumed temperatureā€™s (happy? :wink: ) as low as 30.

SOP in one airline was not to go below 30.

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Right on! The CFM56-3B/C series engines are flat-rated to ISA + 15C at sea level, so the minimum assumed temp (near sea level) would indeed be 30C for the 737 classics. :+1:

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If you use current OAT, FLEX will give the same thrust output as TOGA. FLEX is used to ā€œde-rateā€ by telling the FADEC that itā€™s warmer outside, the FADEC will then limit the N1. It reduces engine wear but at the cost of performance, but counterintuitive maybe but the aircraft actually uses more fuel when selecting a de-rate.

You can see from the graph below, if you go to the right (up in the temperature) the resulting thrust will be lower.

image

Aircraft I have flown and am currently flying we call it de-rate even though the terminology might not be right. In ATPL(A) theoretical knowledge examination its also called ā€œde-ratingā€.

I see a lot of people mentioning field length and atmospheric conditions, there are for more factors such as obstacle / terrain clearance, minimum climb gradient (even without any significant terrain / obstacles) etc. You canā€™t simply say, just add 20C for short runways or 40C for long runways, besides there are situations where the use is forbidden such as:

  • Contaminated runway
  • Thunderstorms in the area
  • Windshear reported / anticipated

Maximum engine ā€œde-rateā€ is 25%.

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Just to be sure, wheel brakes and spoilers are automatically deployed in case of a RTO, the thrust reverser are not automatically deployed however. Without the auto brakes armed you need to use max manual braking. Not 100% familiar with the A320 but on most aircraft you can actually stop shorter with max manual braking, assuming max manual braking is applied immediately.

Thatā€™s why the altitude window should always reflect the cleared altitude / level and not the ā€œfinalā€ altitude / level.

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