Full scale: Mil Mi-26 Halo
The biggest one
Actually not the biggest ever, but the biggest still operating and was in serial production. It cannot be believed how massive it is until you have seen it in real life. We have. Astonishing.

The helicopter itself is about 28 tons, however the maximum take-off weight is around 58 tons. The rotor diameter is 32 metres made up by EIGHT blades, even the tail rotor has got 5 blades. The helicopter is as big as a Boeing 737 without wings. And to be honest it has got a more airplane like shape than a helicopter around the cockpit.

And it is hungry indeed. Not the best choice to take a sightseeing. This is not the helicopter you will fuel at the closest petrol station, because it is likely, if the petrol station sold kerosene, the ground tank would not be enough. Usually the purchase limit is £100 pounds, this amount of fuel is enough for less than 2 minutes. The fuel consumption is 3700 litres hourly, with other words: 60 litres in every minute. Typical start-up time is 15 minutes, a typical monthly income is not enough even to take off. Yes, it is costly to fly, but the original aim wasn't entertaining people.

The helicopter followed the typical Russian approach:
When the helicopter was designed, a tank had to fit inside. But you can find the whole story on Wikipedia - more or less accurate.
I have never seen these helicopters before. I knew Halo is big indeed, I knew its dimensions, and even so, I had no imagination its measures. This helicopter was supposed to arrive to Hungary for filming the Die Hard 5. Ooops one more secret: almost the whole film made in Hungary. At this time, We were based at the Budaörs Airport, which is rather an aerodrome than an airport. The chief of the aerodrome told us: the Halo will come. It was a top secret.

The helicopter was supposed to be repainted for the film in the large hangar. The first sign of the massive dimensions was that, when the chief of the hangar climbed up above the big gates with a measure tape, and he shaked his head. It will be a problem. This gates are 8 metres tall. But the helicopter cannot fit in. 8 metres is more than the height of a typical Victorian house. And the helicopter cannot fit in. I asked them, how tall the helicopter is. 8 metres 15 centimetres without the tail.
Then the big day has arrived. We were waiting for something loud, like a Chinook. Then the helicopter appeared on the sky - with no loud rotors, the engines were much louder, like an airplane. Honestly, the helicopter has no helicopter sound at all. The 8 blade rotor head rotates 116 times in a minute, and the blades, like a wind ripped umbrella, leaning upwards.
We were standing about 150 metres far from the landing helicopter. First gear touched the ground, then the second one, finally the nose gears. And during this time we were wobbling in the rotor wind. Everything happened like in a slow motion film. Finally the engines shut down, blades stopped spinning. About 100 others and we walked closer to the Belorussian helicopter, well, the top secret didn't get a success story. And indeed, the helicopter was massive. We felt like ants running around a car.

The helicopter inside in the compartment area could host a dance party with no problem. 100 people could fit in and next to them there was a space still. The cockpit like an office. It is a typical 5 people crew setup, with four individual "desk", but if one crew member wanted to handle a paper note to another one, he had to stand up.
The main gears - yes, those tiny wheels beside - reach my elbows. And the a crew member at the rotor head looks funny.
Once the Belorussian crew wanted to make a deal with me, exchanging my T-Rex 600N to the Halo. I refused the deal, telling them: "sorry, I cannot fuel it.".

The aerodrome crew could manage to put the helicopter in, but the tail was outside all the time like a huge windmill.
How big is the tail? The helicopter was escorted by a Bo-105, which is also not a small helicopter, like a Robinson. It has got average size. But its main rotor diameter was smaller than the diameter of the tail on the Halo.
Finally the helicopter got repainted, took off at Budaörs, made the film causing one bigger not intentional fire at one of the scenes, came back to Budaörs. Then few days later it has left Budaörs washed down as it was when arrived.
Just one side note about the Die Hard 5 and this helicopter: you cannot hear the real sound of the helicopter in the film, because the sound crew didn't find it too helicopterish. That sound comes from a Black Hawk.