How can a helicopter show up at 29000ft, 547kts at Flightradar24? Today I observed a strange flight on Flightradar24, a helicopter departing HAM and traveling at altitudes up to 29000ft and speeds up to 547kts which seems to be way beyond the specifications of a helicopter.1

The altitude and speed were quite constant on this level between Hamburg (ATD 16:15) and Frankfurt (about 500km from Hamburg, after 30 minutes flight) and then it began descending and slowing down. 


The details in normal resolution for better readability:



About 17:00 the symbol didn't move anymore and the helicopter was now down on 2875ft and 177kts near FKB (Karlsruhe Baden-Baden) and then disappeared.

I checked the registration and is indeed the Agosta Westland AW139 shown on the picture.  

Does anyone have an idea how this could be. Usually, the data on Flightradar seems to be reliable, but a helicopter at 547kts seems odd.



1. According to Wikipedia the Agosta Westland AW139 can travel up to 306km/h (165kts) and has a service ceiling of 20000ft.

edit: speed was 547kts, not 247, added image with details.
@mins answer contains good information, however the conclusion that the mistake is in the Flightradar 24 database is not correct. 

It is not Flightradar 24 that has a database error:


  30040D IS I-PTFT it is NOT I-MOFI F2TH I-MOFI is miscoded on one box
  and using 30040D incorrectly. I-MOFI is 30047D please change it back!
  Why was it changed in the DB when I-MOFI was correct in the DB, I
  thought miscodes were not allowed anymore?


What this says, is that the 24 bit Aircraft Address (a.k.a. the Mode S address) 30040D belongs to the aircraft with the registration I-PTFT. 

The registration I-MOFI has the 24 bit address 30047D, but the quote says it is miscoded on one box (transponder). 

Flightradar 24 receives the Aircraft Address with the ADS-B messages from the aircraft and uses the database to find the aircraft associated with the address. 

From the screenshot it can be seen that the address they receive is 30040D. In their database, this is correctly linked to the I-PTFT helicopter. 



The fault is with the aircraft with registration I-MOFI; it transmits the 24-bit address 30040D while it should have transmitted 30047D. The transponder has the wrong 24-bit address encoded into it.