Jump to content

AS350 SD2 with FDC - power check procedure

Recommended Posts

Can you please help me, how do you understand correction factor reducing OAT by 4°C for power check performed on SD2 equipped with FDC filters (ref. RFMS 1350-2200)?

Engine performance physically is reduced when FDC is installed. So based RFMS it is allowed to operate helicopter conditionally in the case when power check results doesn't meet Soloy SD2 RFMS Basic Performance, then several conditions must be met:
- more often power check
- power check results with OAT 4°C reduction must be positive. But it doesn't make sense in my opinion because when we reduce OAT by 4°C the result will be more negative vs. basic performance, but should be more positive to compensate FDC influence.

So I wonder if my understanding is correct. How do you understand it?

Link to comment
Share on other sites

It’s been a while, and only a pilot:  

-but if I remember correctly, that correction factor is only applicable if your maintenance department had determined that it is the filter that is the problem.  And not engine related.  

-Make sure you are pulling a limit during the power check. ie 94% TQ.  There are some fight parameters that don’t fit within the power check chart, if you aren’t pulling near  a limit. 

-If it’s a new filter or recently been cleaned and lubed, make sure it’s been set out to dry off for the appropriate time and not too wet. Blue oil dripping around/in your engine intake isn’t a good thing. 

-Also in colder climates, it’s common for pilots to leave the heat valves open a crack so they don’t stick.  Make sure they are closed tight for the power check then 1/2 crack them open again once power check is completed. 

Link to comment
Share on other sites

Hello Tom,

When using B2 Sand Filter power check, the Ng diagonal lines are shifted to the right (vs the power check without sand filter), making the test "easier" to pass, but I guess it's "too" easy for the IBF, so a "fine" of -4° OAT is given to make the power check just a little more difficulty to pass.

Does that make sense?

Soloy LLC, don't really have a power check with sand filter in their supplement, so I'm not sure of their power check procedure when IBF (or sand filter) is installed.

However, if you check Soloy LLC supplement, on page 2 is specifically says sand filter not approved (see attachemnt).



Also it says when IBF installed there's no change in performance. (see second attachemtn)


So my conclusion is that with SD2 and IBF, you use their regular power check graph with no 4° reduction.

Link to comment
Share on other sites

Hello Zazu and Saifan Pilot, thanks for your advices!

Of course I mean conditional power check when basic performance is not assured and IBF is the only reason of lower performance.

IBF RFMS Nop. 1350-2200 is applicable for SD2 with no reference to Sand Filter in difference to analogical RFMS 1350-1200 for AS350B2 that refers to Sand Filter Sup.14. So because of this that Sup.14 is not applicable to SD2 there is no such reference in power check procedure. Please look at below:image.png.0621e6e905bfaa7fa75e1030be22cb8f.png
We need to refer obviously to Soloy RFMS becasue the helicopter is powered by LTS101-700D-2 Engine. So it is why I don not understand the OAT 4°C reduction when the result is more negative then before.

Please see analogical procedure for AS350B2 powered by Turbomeca Arriel where procedure refers to Sand Filter RFMS and it makes sense as Saifan said.


Link to comment
Share on other sites

4 hours ago, Heliian said:

Try the power check with the bypass door open, if there is an increase in margin then you can look to your filters for clogging, dirt and too many "repairs".  

Ough, it could be the last positive results on this engine :P We usually find sand, grass debris and other particles in the area between bypass door. Moreover on EC135 rotor brake is mounted between doors so you can imagine engine compressor or diffuser when it sucks this dust with all other debris 🤔 The scheduled cleaning of this area is a good idea.

The problem which I have on SD2 concerns proper calculation with reducing OAT by 4° when basic power check is below the limits and IBF is the only reason for this. According to RFSM I can continue operating using some factors (see on the screenshots above). But the result is even more negative then before when I repeat calculation with these factors...

Link to comment
Share on other sites

You are not wrong. Our SD2s had an AFS in it because of FDC’s intricacies.

I have attached the AFS supp 0. It says no changes to procedure.

Also attached is Soloys flight supp chart.

If you use their example of an 820 with an OAT of 15 and then recalculate with an OAT of 11 you get just about 800 meaning you now fail your power check by -20 more.

I guess this is why the authorities in the US have been clamping down on the filter companies for using manufacturer’s charts with “work arounds” instead of spending millions in flight testing and data collection to create their own charts. 

Sorry Tom, no answers from me.



Link to comment
Share on other sites

23 hours ago, tom_pilot said:

Ough, it could be the last positive results on this engine :P We usually find sand, grass debris and other particles in the area between bypass door.

Uh, there might be a stray blade of grass or dust but if you have that much #### inside your housing then you need to be more diligent with inspections and cleaning,  possible that the seal is no good and needs to be adjusted.

Cant speak on the 135 though, but again, regular cleaning helps.

The bypass system needs to function properly and shouldn't be at risk of ingesting a damaging amount of fod.  

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...