A320NEO lower Vapp in CONF FULL
 

Hi all,

At the airline I work we started operating A320 NEOs with PW engines a few months ago and I noticed that they have a much lower approach speed in CONF FULL than the CEOs we operate (MNSs 7500/8800 with, as I understand, the same wing). What's the reason for such a change? I know the new engine comes with a new pylon but still a 6/8kt difference is a lot to me. CONF 3 speeds remain similar though.

Thanks in advance for your answers!

You beat me to it. I noticed in CEO the Vref flaps full is appx. = GW+70 while in Flap 3 it is Flaps Full+5kts. For example GW 60T+70=130kt with flaps full and for flaps3 it is 130+5=135kts. In the Neo Flaps full is GW+65 i.e. and60+65=125kts but Flap3 is Flaps full+10kts. i.e. 125+10=135kts. I can guess 5kts increase over Flap3. It is to prevent reduction in the tail clearance.

It's a possibility. I also noticed the NEO flies with a slightly higher pitch attitude in CONF FULL (around 4/5º vs 2.5/3 on the CEO), maybe AOA is not as critical as in the older versions.

Flap full angle in the NEO is 40 degrees (same as the A319) whereas the CEO is 35 degrees. Slat angle is the same for all.

CFM56 A320s have 35 degrees, IAE have 40 (same as the NEO).

learn something new every day. Cheers :ok:

Thinking a little deeper the Neo sharklet effectively increases wing span which should reduce the Vs1g leading to reduction in 1.23Vs1g which is Vref. But CEO with or without sharklets seems to be treated as same. As even in GSmini the Neo increase in IAS is only 1/3rd of the ∆wind but in CEO it's 100%.

Just for interest, I computed on Ipad the landing performance: The A320 CEO and A320 with sharklets have exactly the same VAPP for conf 3 and conf Full. With a landing weight of 60T it was VAPP of 135kt in F3 and 138 for conf Full.
the 320 NEO was Vapp 140kt conf 3 and 130kt conf full.
Weird that in conf Full the speed is actually 5kt lower but in Conf 3 it’s 2kt faster. Any explanation for that? the flaps and slats extension are exactly the same. IAE and PW engines.

I also compared the A321 CEO versus the NEO and for a landing weight of 70T VAPP conf 3 was 146 kt & 141kt conf Full versus 146kt conf 3 and 135kt conf full on A321 Neo. 11kt difference! But this is explained by the difference in flaps extension difference in Config Full the Neo has flaps down to 34 degrees versus only degrees for the 321 CEO.

You may be flying CEO in IAE and Neo in CFM. Compare Vref CFM CEO to CFM Neo. In CEO for 60T Flap full is 130kt and Flap 3 is 135 and in Neo it is Flap full it is 124kts and Flap 3 it is 134kts. As I said before the Neo Sharklet increases wing area so Vs1g will.be little less so 1.23g which is Vref is 5kts less than CEO. But in Flap 3 as it is tail clearence is less so they have added 10kts instead of 5kts as in CEO.
I think 321 has double slotted flap that keeps the attitude low.

Hi Vilas. We only have IAE engines and PW for the NEOs.
And when I compare the IAE 320 sharklets VS non sharklets the speed are exactly the same.
But the Neos, Vapp flaps 3 is faster which with your explanation about the tail strike clearance makes complete sense to me, But why the VAPP config full of the NEOs is lower than the 320 classic with Sharklets?:confused:

In CEO sharklet mod Airbus appears to have only taken advantage of reduced 2 1/2% something fuel burn but hasn't done any other changes to GSmini factor or Vref reduction.

So since it’s the same wings as the NEO; Just the engines are different why the VAPP conf full is significantly slower on the NEO? For a weight of 60T with calm wind NEO vapp conf full is 130kt and CEO with sharklets is 135kt.

My QRH confirms the observations above, -232 to -271N. Admittedly I supposed a typo in pinteam's FlySmart speed-definition tables for a moment (surprisingly possible).

SPECULATION: During flight testing Airbus discovered the possibility to certify a lower speed and grabbed the chance as the whole idea behind landing is to stop the aircraft. Whether or not the possibility was there already on the sharkletted CEO's but such testing was not done or not explored for commonality purpouses is a speculation squared.

A nice find. The Vmca is higher on the -271N, green dot as well if only by a little.

F and S remain identical, while Vls CF3 is higher by 2 kts, that is somewhat perplexing.

Nice catch, I am checking CFM/CFM LEAP data and the VMCA is 4 kts higher on the latter. Other than that, I only find a significant difference on Vref between CEO/NEO as discussed above, ie. 6 kts lower on the NEO, but that is due to the higher flap angle.

In terms of m/squared the CEO/NEO sharklets area is the same... unless I am missing something.

What I said applies to Ceo sharklet as well but Airbus doesn't seem to have considered that for Vref or GSmini factor reduction.

I was under the impression that Vref reduction came from the higher CONF FULL angle of the NEOs compared to the CEOs but as You mention the GSmini factor reduction as well is likely to support the theory of something that was not developed at CEO stage.

In flaps full Ceo IAE flaps full has 40° flap and Ceo CFM has 35° flap but Vref is same. However GD speed is different IAE it is GD= wt×2+80 while CFM is wt×2+85. Even CFM leap(neo) is same.

a) Vmcl(*applies for Vmca too, but since we're discussing the approach phase Vmcl is what I had in mind already in the post above) and the Optimum Single Engine speed (green-dot) being higher for the NEO: While rated at the same 27.5k, the higher drag of the failed engine with a larger diameter could suggest the reason behind the increase of the speeds.

vilas in my book that also covers the greater GD on CFM compared to IAE. But it is the other way around for Vmca! :(

b) Flap angles.
ceoCFM (sharklets or not) Full = 35°.
ceoIAE (sharklets or not) Full = 40°
neoPW (sharklets) Full = 40°
neoLEAP(sharklets) Full = 40°

Assuming higher residual thrust on all compared to CFM, the choice for a higher flap angle could arise either for handling qualities at landing (too slippery) or the need to have higher drag to assure necessary core speed to meet the go-around engine acceleration requirements. The steeper angle causes more noise and fuel burn, surely a decision taken not without a serious cause. (Fun fact: the Full-flap limiting speed remains identical,177 kt.)

The question why on neoPW-shark is the Vref 6 kt less compared to ceoIAE-shark still stands, IMHO.

GD speed for CFM Neo or Ceo is same i.e. five kts higher than IAE. To have higher GD speed the drag has to be less and not more. I have a graph by airbus thrust against altitude CFM Vs IAE in that it is mentioned CFM gives higher thrust at higher altitude while IAE gives at lower altitude. That is why on approach IAE may be requiring the extra flap setting for higher drag to keep the thrust out of idle. During taxiing also IAE tends to run as compared to CFM. On the higher level CFM OEI ceiling is four to five thousand feet higher than IAE. Also there is a distinct flattening of the one engine ceiling curves around 25000ft even at various ISA deviations.