Charts...

[Aser]

1-Does your twin(specify type) have a drop down height chart?
2-Does your twin(specify type) have a single engine hovering ceiling chart?

Yes,No,Why?,comments


Thanks.
Aser

[IHL]

Hi ASER: I assume (maybe wrongly) that you mean by "drop down" as being able to maintain a MEA over high terrain after an engine becomes inoperative.

The chart to use-depending on regulatory authority-would be the 30 min power [OEI] forward climb performance chart. If your performance matches ZERO ROC or better your good to go.

I'm not aware of any current twin helicopter that has single engine hover performance. Perhaps the AB139 or S92 does, but I don't know.

[Aser]

IHL you're assuming it right. ;)
I've used the ROC chart in the same way you explain but I was wondering is there are specific tables for the "drop down" or single engine hover in any helo.
Is it just because you can extract the data from other charts?
Nick can you comment?


IHL: "depending on regulatory authority" <- Did they say what charts to use?

Thanks.

[JimL]

I think you need to be clearer whether you are discussing 'drift down' or 'drop down' they are totally different.

Drift down is the ability to fly at an altitude with the knowledge that, if you lose an engine, you can drift down to maintain a safe altitude - whilst clearing obstacles during the descent by the prescribed distance. This can be calculated but the glide angle has to be used (i.e. wind has to be known); unless it is done offshore when it is a simple calculation.

Drop down is associated with Category A procedures - it represents the one-engine-inoperative descent from TDP to a point (usually called min-dip) from which obstacle clearance can be assured and continued take-off is possible. Drop down graphs are provided by manufacturer which have these type of procedures; where elevated helideck/heliport procedures are provided the deck-edge miss is guaranteed by the procedure and drop down below the take-off site is permitted.

Most twin engine helicopters can hover on one engine - only the best can do it at close to MAUM. For civilian helicopters, the AB139 gets the prize and most of the clever small twins (EC135, MD902, A109 - power and grand, Bell 429 etc) are getting closer (at sea level). Most States require OEI HOGE performance to be calculated and used when CAT hoisting is being performed.

[Aser]

Thanks JimL, I didn't know the difference, I was asking if there are "drift down" charts.

Regards.
Aser

[Shawn Coyle]

There probably won't be any charts labeled 'drift down'. They will be more probably the required-by-regulation 'rate of climb' charts. They just happen to show negative rates of climb...

[EESDL]

If my memory serves me correctly (it rarely does) JAR requires you to have 50'ROC at this stabilised ht on one engine.

[212man]

Missed this one!

Naturally, Jim and Shawn are correct, along with EESDL.

You can produce your own charts if the FLM ones are not user friendly. The thing is to determine what fixed parameter you want (RoC, Weight etc). It takes a lot of time extracting the plotting points, but you can then produce a more user friendly result. e.g. for the EC-155 I produced a single graph to determine PC1/2 en-route weights from 4 separate graphs in the FLM; much easier to use!

It is also correct that many older types can hover OEI; just not necessarily at the weight you'd like them to! :\