Does this speed and descent rate look right?

[Teevee]

I took this off the forum of my local airport, it's in the movements thread where guys track incomings and outgoings on the SBS thingies. I've removed the airline and specific airport but I just wanted to ask whether you who know what you're doing (I'm SLF!) think the descent rate and speed for the given altitude look a litle excessive? Maybe I should tell the guy to get his SBS recalibrated!

Altitude : 1798 m - 5899 ft
Ground Speed : 540 km/h - 336 mph - 292 knots
Vertical Speed : -819 m/min - -2687 ft/min (DESCENT)

[Avman]

Depending on type, not excessive at all if:

- No speed restriction

- relatively expeditious descent required

[Wizzaird]

Quite common to see this sort of RoD if aircraft has previously been kept high (happens a lot at EGCN in order to keep the aircraft in controlled airspace) and the speed looks about right too.

[Northbeach]

The cabin is pressurized and the system is compensating for the descent to arrive at the set altitude for landing. The people in the back should be quite comfortable at the rates you quoted. For a jet profile it is normal. If it were an unpressurized single or twin it would get your attention.

There are several "odd" thing in your example. For one the aircraft is > 6,000' and descending at close to 3,000 fpm. Even assuming a sea level airport the rate of descent for the altitude above the ground does seem to be excessive to me. I would suspect the ground proximity warning system to start "talking to me" under those conditions.

The rate of descent is somethig you will see in a jet. However, the altitude above the ground for this rate of descent isn't something I usually see. It is the combination of the relative closeness of the underlying terrain and the rate of descent that does make this a little bit odd.

At 5,899' MSL assuming a 3:1 profile the aircraft should be approximately 17 NM from touchdown (assuming a SL airport and a landing in progress). An airspeed of 289 KTS seems excessive. In most places I know of below 10,000' the maximum airspeed is 250 KTS. So the speed seems fast for the altitude and the distance from the airport.

Many assumptions here; is the airplane landing or taking part in an air show? Is this a normal operation or some special demonstration, test or emergency in progress? Or is somebody out for a joyride in their "toy"?

Below 10,000' I am usually at or below 250 KIAS. This airplane is faster than that (unless some large tailwind in play). At 17 NM from touchdown I am usually configuring and slowing down. Below 6,000' my descent rate is usually well below 3,000 FPM.

[Avman]

There are several "odd" thing in your example. For one the aircraft is > 6,000' and descending at close to 3,000 fpm.

Unless it's a B727 of course ;)

[Teevee]

Thanks guys! I don't know if Wizzaird is aware that his comments are particularly pertinent! It was an A320 at an airport of his knowledge by the sound of things! It was the speed and RoD at that altitude that drew my attention to it given that it probably wasn't much more than 20nm from touchdown. But thanks for clearing it up!

[PAPI-74]

@ 330kts (5.5 nm/min) use 3 x the Flight Level you need to loose and 1500 fpm.

e.g. - you need to loose 10,000. This will take you 30 nm at 1500 fpm - or 60 mn at 750 fpm

e.g. - you need to loose 8000. This will take you 24 nm at 1500 fpm - or 48 nm at 750 fpm or 32 nm at 500 fpm.

...and so on.

[Groundloop]

It's a Groundspeed of 292 knots - not the airspeed. Could be a good tailwind.

SBS does not do any calculations - all it displays is the information transmitted by the aircraft.