I have a slight problem in that my cockpit keeps an alarm going on when it thinks I am going too slow on landing.

The speed it has an issue with is 138kts (too fast if you ask me), otherwise, the cockpit gets an alarm, even when I'm just seconds from landing.  It is regarding the Aerosoft A320.  I have seen plenty of TV programs to try and teach me how fast I should be landing, and they all tend to say slower than 138kts!

One thing on my mind is maybe I have too much fuel left in the tank, and therefore the aircraft needs a higher speed to land safely.  What sort of speed should i be landing at - or is this down to another problem?  I've tried fuelplanner.com, but my aircraft are all VERY heavy if I use that page.

Thanks, Gaz

Usually that means something isn't configured correctly.  You have gear and flaps down?

@Gary McCluskey, sounds like you’re too heavy because you’re loading too much fuel. I’ve been using PFPX for years with the PMDG738 and no such problems being too heavy when landing. http://www.flightsimsoft.com/pfpx/

Okay, it's almost certainly that you have too much fuel on board for a minimal reference speed, and by that I mean more fuel than most tutorials will typically recommend to have on board, because tutorials tend to be based around the 'perfect/ideal' scenario. This does not however, mean that a higher reference speed is 'wrong'. The landing reference speed is based on a lot of things, including your weight, weather conditions, runway elevations etc. 

Not every airline flies with minimal fuel and refuels at the destination on the spin, most do, but not all, some 'tanker' fuel to their destination to aid in a fast turnaround. Vueling is for example an airline which does this on their flights between Spain and the UK. Because of this, there is no typical speed in real life for landing v-ref, it depends entirely on your exact situation, and so it may well be that for every scenario you have tried, 138 knots was the correct v-ref speed. So, first let's ensure you are putting the right info in and then after that, we'll have a look at how to calculate the correct fuel for a trip in the A320 so that the v-ref is not too high...

Assuming your flight plan is all in and you are flying along nicely and thinking about your landing preparations, at about 80 miles from arrival, you should start making sure everything is prepped for landing. First thing you want to do is find out the wind speed and direction at your destination, and the temperature. You can tune the ATIS for the arrival airport, or look on your weather add-on program, or now - thanks to the recently-released REALVOLMET EUROPE - you can tune the Volmet station for your destination region and get that data a bit sooner. Keep in mind that you ignore the gust speed and utilise the lowest wind speed stated, i.e. if it says 'winds 270/20-25 knots', then you use the lower value, i.e. 20 knots.

With that info to hand, you choose the PERF APPR page on the MCDU and enter the QNH, temperature and wind at your destination. When you know the runway you will use, you insert the MDA (decision height). The approach charts will tell you that, but the value varies with the airports RVR indicator equipment (runway visual range gear), so if you're not sure, put 200 feet, as that's a fairly good average value for many airports and will do unless there are some hills or structures which specifically need avoidance.

Choose your flap setting. Keep in mind that if there are gusty conditions, smaller flap values and higher speeds are recommended. This is because the aircraft needs to keep up the inertia in gusty conditions in case there is a wind speed drop on finals, so, at lower flap settings your v-ref speed will be higher to give you a safety margin. Bob's yer uncle. The landing v-ref should be correct based on the present conditions and your landing weight. You can go a bit higher than the landing v-ref speed on finals and lots of pilots do so they've got an even bigger safety margin if the winds are particularly gusty or they suspect there might be a wind gradient or wind shear, but you'll get an audio alert if you go lower than the v-ref.

Oh and don't forget to set the go around page and the radio nav page. Also, set the SEC F-PLN page to an alternate runway or destination so that you can switch to that if there is a last minute ATC runway assignment, rather than having to faff about entering stuff when you are busy flying.

Now let's look at fuel planning. Below are the exact ICAO Annex 6 fuel requirements for airliner operations:

Taxi fuel.

Trip fuel (to reach intended destination).

Contingency fuel (higher of 5% of "trip fuel" or 5 minutes of holding flight).

Destination alternate fuel (to fly a missed and reach an alternate). Final reserve fuel (45 minutes of holding flight for reciprocating engines, 30 minutes for jets).

Additional fuel (if needed to guarantee ability to reach an alternate with an engine failure or at lower altitude due to a pressurization loss).

Discretionary fuel (if the pilot in command wants it, but this is not compulsory). 

The A320 (the original model, not the NEO which is more efficient) has a fuel capacity of between 6,300 and 7,835 US gallons (or about a maximum of 30,000 litres) depending on the model and fuel tankage fitment (some A320s have an extra tank which takes up some of the space normally occupied by the rear hold near the bulkhead). It uses about 2.569 US gallons (9.76 litres) for every mile it flies. These are average figures, as noted, fuel capacity actually varies between A320 models quite a bit and how much of that capacity can be used depends to some degree on the temperature since the volume of fuel changes at different temperatures.

This means that with a range of about 3,300 miles, the Aerosoft A320 (with a fuel capacity of 6,300 Gallons), 63 gallons on the P3D/FSX fuel page for the Aerosoft A320 equals 1 percent of its total fuel capacity. Which means it can fly an average of 33 miles on 1 percent of its maximum fuel load. This is a convenient number because it works out to approximately 3 percent of fuel for about a hundred miles of flight.

So it is pretty easy to calculate how much fuel to throw into your Aerosoft A320. For example, let's say you are flying from Manchester to Almeria, which is a distance of about 1,000 miles. Using our handy 3 percent equals about 100 miles, we can use the following easy formula for a 1,000 mile trip of: 3x10=30. From this, you know you're going to need about 30 percent fuel on board to get to Almeria. Once you know how many gallons that is (off the top of my head that is roughly about 1,900 gallons, but you could check it on the fuel menu in your sim), you now know 1 percent of your trip fuel is 19 gallons, and from that, you can work out your extra percentage of fuel for all of the ICAO Annex 6 legal fuel requirements, and that means you can carry the exactly correct amount of fuel and know you are okay, which means you can have a lower landing v-ref speed.

So you can tell from that when people put 100 percent fuel in their A320 for a trip that really should only need about 40 percent of capacity, it's obvious that their v-ref landing speed is going to be on the high side of things.

Edited March 22, 20206 yr by Chock

Chock,
That is a wonderful primer and certainly took a long time to construct and write so well.  It should be archived.  I know he mentioned concern about his fuel load. But why did you not first ask him about his actual fuel load?
Not arguing at all.  Just seems like a logical question.

Edited March 22, 20206 yr by fppilot

138kts is fast but correct for an A320 at MLW.  A heavy A321 is even faster at 146.

Another important point is to always consider that the loadsheet and or the data entered into the FMC could be wrong.

If the pitch attitude isn't between 0deg and +2deg (on 99% of the airliners) it's a good indication that something is wrong with the calculated speeds/weight.

If you get this 'alarm' seconds from landing, it would be nice to know what kind of alarm this is.

Sound more like the middle or inner marker to me.

If you are too slow you should get s 'SPEED SPEED' aural warning. 

 

Edited March 22, 20206 yr by FDEdev

Chock, thanks for a very well written explanation on fuel planning. Easy to follow and understand 👋

Regards

G

18 hours ago, Gary McCluskey said:

The speed it has an issue with is 138kts (too fast if you ask me)

Not sure I agree with this. I regularly see Approach speeds in the 135-140 KIAS range? 🙂
138 KIAS is what I got as Vapp with the FSL A320 on my last flight (CONF FULL, winds calm, so no ground speed "mini" compensation).
Standard 3 degree ILS, pitch 2 degrees up (approx.).

And one easy "mental math" check to verify against fuelplanner.com and your  A320 fuel load,  try these generic numbers and take the 1.000 NM trip for example (Manchester - Almeria) 
A320 IAE engines:
TAXI: 200kg
CLIMB to CRZ ALT : 1700 kg
CRZ : 2300 kg/hr  x 2 hrs = 4600 kg (TAS 450 KTS)
DES from CRZ ALT : 300 kg
APPR  : 200 kg
TRIP FUEL:  6.800 kg
--------------------------------
Cont. (3% EASA OPS): 205 kg
--------------------------------
FINAL RSV : 1.000 kg (30 mins)
--------------------------------
ALT FUEL 1.300 (30 mins away)
--------------------------------
RELEASE FUEL  9.305 kg (Not accounted for winds, so beware)

Is this perfect and can be used all the time? no not at all, but they are close enough when you quickly want to crosscheck a fuelplanner's output.

For comparison. PFPX gave me 8.900 kg with all data being fed into the software with accurate FSL A320 profile (taking account winds, temp, SID/STAR and Cost index)

Happy flying!

 

 

Yes a VApp of 138 is quite normal for a A320...it can go even higher if you have a strong headwind and heavy aircraft.

15 hours ago, regis9 said:

Yes a VApp of 138 is quite normal for a A320...it can go even higher if you have a strong headwind and heavy aircraft.

A V_APP of 138kts means an actual weight of 63t which already close to MLW. At low weight V_APP is only 118kts. 

13 minutes ago, ryanbatcund said:

You have gear and flaps down?

Yep

4 minutes ago, Ray Proudfoot said:

sounds like you’re too heavy because you’re loading too much fuel

I've tried the same journey with less fuel on landing ( just over 2) and it's fine, but still fast.

Gaz

@Chock - thanks for that. Quite complicated, but I'll go through it.

Gaz

5 hours ago, FDEdev said:

A V_APP of 138kts means an actual weight of 63t which already close to MLW. At low weight V_APP is only 118kts. 

I got 139 Vapp with actual LM of 61.9 metric tonnes (Max LM 64.5) in the FSL A320, wind conditions 24004KT, 25 ft. field elevation on the airport.