For a moment Sirius looked confused, because did Philip really think that there was something wrong with the broom? Was it broken? Why did he think it looked like it wouldn't fly? Then he remembered that Philip hadn't seen anyone flying on a broom before. All the charms were invisible and maybe it wasn't obvious how they worked, like it was with carpets.
'It really does!' he assured his new friend. 'It's enchanted with charms to make it fly and make it comfortable. You'll see.'
After he was finished with the safety checks, he considered the questions seriously. 'I don't think you have to do calibrations every time,' he said reassuringly. He didn't really know what they were himself, except that they were complicated and when you went to Hogwarts you had to do lots of them before you were allowed to fly for Slytherin and it sounded boring. It was good Arcturus just did them for him. 'Quidditch is a sport people can play when they're flying. It's really good but you need lots of people for a team.'
Now came the important moment. Sirius set the broomstick down on the ground – carefully, he wasn't allowed to just drop it – then stood up again, held out his hand and called, 'Up!' The broom rose smoothly up in to a low hover, and Sirius sat himself on it sideways, before letting it climb higher still. 'See! It flies!' Then he swung one leg over the broom, and gave Philip a little wave as he flew around him in slow, looping circles.