Node.js Module async.series not working properly - asynchronous

Question

I'm working on MongoDB 2.6.9 and NodeJs 0.10.37 and I have a collection vols which means flights.
According to my previous question, I have a large collection vols with documents like these samples :
> db.vols.findOne()
{
"_id" : ObjectId("5717a5d4578f3f2556f300f2"),
"Orig" : "PTH",
"Dest" : "GMP",
"Flight" : 126,
"Stops" : 0,
"Seats" : 169,
"Ops_Week" : 3,
"Eff_Date" : "2016-04-14",
"Mkt_Al" : "XX",
"Dep_Time" : 1110,
"Thru_Point" : "",
"Arr_Time" : 1600,
"Block_Mins" : 230
}
The next document, refers to a flight with stop.
> db.vols.findOne({Stops:1})
{
"_id" : ObjectId("5717a5d4578f3f2556f301c5"),
"Orig" : "CIM",
"Dest" : "LKR",
"Flight" : 7756,
"Stops" : 1,
"Seats" : 70,
"Ops_Week" : 2,
"Eff_Date" : "2016-04-11",
"Mkt_Al" : "YY",
"Dep_Time" : 1655,
"Thru_Point" : "BHU",
"Arr_Time" : 140,
"Block_Mins" : 345
}
And I have to calculate a score for each document with this formula and insert it into the document as a new field :
I Have tried this algorithm, using the 'async' module with series method but I didn't get my desirable result ...
var mongoose = require('mongoose'),
express = require('express'),
async = require('async'),
Schema = mongoose.Schema;
mongoose.connect('mongodb://localhost/test');
var volSchema = new Schema({},{ strict: false, collection: 'vols' }),
Vol = mongoose.model("Vol", volSchema);
mongoose.set('debug', false);
mongoose.connection.on("open", function (err) {
if (err) throw err;
var bulkUpdateOps = Vol.collection.initializeUnorderedBulkOp(),
counter = 0;
Vol.find({}).lean().exec(function (err, docs) {
if (err) throw err;
var locals = {};
docs.forEach(function(doc) {
locals.c1 = 0.3728 + (0.00454 * doc.Seats);
locals.c3 = doc.Ops_Week;
if (doc.Stops == 1) {
async.series([
// Load doc with first leg first
function(callback) {
Vol.findOne({
Mkt_Al: doc.Mkt_Al,
Orig: doc.Orig,
Dest: doc.Thru_Point
}).lean().exec(function (err, flight) {
if (err) return callback(err);
locals.first_leg = flight.Block_Mins;
callback();
});
},
// Load second leg doc
// (won't be called before task 1's "task callback"
// has been called)
function(callback) {
Vol.findOne({
Mkt_Al: doc.Mkt_Al,
Orig: doc.Thru_Point,
Dest: doc.Dest
}).lean().exec(function (err, flight) {
if (err) return callback(err);
locals.second_leg = flight.Block_Mins;
callback();
});
}
], function(err) { // This function gets called after the
// two tasks have called their "task callbacks"
if (err) throw err;
// Here locals will be populated with `first_leg`
// and `second_leg`
// Just like in the previous example
var total_flight = locals.second_leg + locals.first_leg;
locals.c2 = 0.03;
locals.c4 = Math.pow((doc.Block_Mins / total_flight), -0.675);
});
} else {
locals.c2 = 1;
locals.c4 = 1;
}
counter++;
console.log(locals);
bulkUpdateOps.find({ "_id" : doc._id }).updateOne({
"$set": {
"Qsi": (locals.c1 * locals.c2 * locals.c3 * locals.c4)
}
});
if (counter % 500 == 0) {
bulkUpdateOps.execute(function(err, result) {
if (err) throw err;
bulkUpdateOps = Vol.collection.initializeUnorderedBulkOp();
});
}
});
if (counter % 500 != 0) {
bulkUpdateOps.execute(function(err, result) {
if (err) throw err;
console.log(result.nModified);
});
}
});
});
At the end I find myself with a result that is the same in both cases, flight with stop or not.
I think that the secend task wich calculate second legs, waits until the calculation of all first_legs, instead of after each first_leg.
Also the insertion of the score must wait until the end of calculating the score for each document, I think bulkinsert should take place after other calculations.
Now I don't know if I should work with async.series or async.foreach or async.parralel or combinate them ...
Please who can help to achieve the above ...