I am a Hong Kong citizen and was looking for a HKG-LHR return ticket. I found an offer from Finnair, of which the outbound flight from HKG to LHR combines two of their flights and has a stop at HEL. Despite being appealing to me, the 55-minute transfer time really concerned me. After I've done some research on their website, I realised that I will have to go through a security check, passport control, and also a health check under the COVID situation. May I know is 55 minutes enough for me to catch the connecting flight? Thank you.
With the two flights on a single booking, it means the airline thinks it’s possible, and will usually do all they can so that it happens (because they have a liability of it doesn’t).
You won’t go through passport control in Helsinki: you are coming from a non-Schengen country, going to a non-Schengen country, there’s no reason for anyone to check your passport there.
If your incoming flight is on time, I would expect deplaning, going through security, and going to your gate to be well under 55 minutes. No idea about the Covid-related checks (I don’t even know if they would actually happen in Helsinki in your case).
Note that if you miss your outbound flight, the airline has a duty to rebook you on the next available flight (there seems to be one about 3 hours later). If for some reason that flight is full or you don’t make that one either then they have to pay for hotel and meals until the next available flight.
So I wouldn’t worry too much. Worst case is that you are delayed (and in that case you may be able to claim compensation for the delay). Best and most probable case IMHO is that it all goes as planned.
As @jcaron has written, theoretically, it should be possible in case your first flight is not delayed. However, I would not count on that. Very recently I had two flights with Finnair (one within the EU, one outside), both were delayed.
If your first flight is delayed, will you be allowed to enter Finland? Currently, due to the pandemic, there is a single cafe working until 10 pm if I am not mistaken (the kitchen closes earlier) in the third (international) terminal. The Helsinki airport is quite comfortable to sleep in there if needed but the single hotel that is in the airport is closed; all lounges are closed as well. Clearly, this is the responsibility of the airline to provide you with the next flight available but I don't know how they will deal with the situation if you are not allowed to enter Finland.