Verb ryk (VB masu) kakeru - used with Transitive/Intransitive verbs - an action/ a state is about to take place- you start doing something but you don't finish that action, so it remains half done = BEGIN TO~; BE ABOUT TO~; ALMOST (DO)~
a). ご飯を食べかけた時に、地震が起きた。 When I was about to eat[/just started to eat] my meal, the earthquake occured. (so I didn't finish the action)
b).父は若い時に、海でおぼれかけたそうだ。 I was told that my father almost drowned in the sea when he was young.
c).雨が降りかけたが、また天気になった。 It started to rain, but it became fine again.
d).オアは開きかけたが、また閉まってしまった。 The door begun to open, but it closed again
ます形 ＋ かける
1. 〜かけている/〜かける：実際に起こる直前 This form takes the meaning of "just as", "just before", or "on the verge of" "about to." It uses verbs that finish or change in an instant (一瞬で終わる/変わること), i.e. 消える、死ぬ、切れる etc.
2. 〜かける/〜かけて: 直前 This form implies the idea that the action had barely begun and then stopped.
Ex. 今日こそ彼に一言いってやろうと思ったが、言いかけてやめた。In other words, "he" never got the complaint. The speaker probably stopped at, "umm... nevermind."
宿題の文作を書きかけたが、なかなか先にすすまないので結局途中でやめてしまった。This person probably got as far as writing their name before quitting.
3. 〜かけの/〜かけだ: 途中 This form means in the middle of an incomplete action. It takes verbs that take time/occur over time (動作が続く動詞), i.e. 食べる、飲む、etc.
In the example sentence that it has been written by (deeana) 雨が降りかけたが、また天気になった。It should be 雨が降りかけたが、またいい天気になった。 I think that it would be better to get these sentence check by Japanese.
〜かける indicated that one has begun an action and is currently involved with it. In almost all cases 〜かけるmay be used in place of 〜かかる, although it expresses a slightly more advanced state (see examples above).
Jonathan: [kaketa] is an identical entry, so i will probably move this example over...