jmt18325 said:
I found the article. I have no confidence in whats it says, but I'll provide it to reinforce that I don't make things up. From the article:
When it comes to the CH-146 Griffon (bottom), a modest life extension program is being considered to upgrade the analog cockpit and potentially improve the engines. This is key for the Griffon’s role as an escort for the CH-147F Chinook (top). Currently, the Griffon cannot match the larger helicopter’s speed. The other alternative, of course, is to acquire a new fleet.
http://skiesmag.com/news/article/Planning-for-power
jmt, I can see why at first glance, the juxtaposition of improving the Griffons engines and the issue of speed vis-a-vis the Chinook could be seen to imply increasing the Griffon's speed. In this case, the writer should have been more clear about the kind of improvements that replacing the Griffon's existing P&WC PT6T-3DE with the PT6T-9 would achieve:
1) increased performance at high altitude and hot temperatures (the PT6T-9 is still "flat rated" [essentially 'restricted' from producing 'too much' power] to a certain HP rating at lower temperatures and altitudes so as to not overpower either the main transmission and/or combining gearbox that adds the input of each of the two 'power sections' together); and
2) better engine management through the use of full authority digital engine control (FADEC), that optimizes through automation, sequences such as engine starting, run-time governing and engine malfunction management.
For the 'hot and high' take a look at the
Pratt and Whitney Canada - PT6T engine information site and scroll down to the chart at the bottom. Note that the FADEC-controlled PT6T-9 outputs the same (or in some cases very slightly less) mechanical power (1855 SHP), but its thermodynamic rating is close to 20% higher than mechanical rating. What this means is that while the governor will keep the engine from ever exceeding its mechanical rating, as the helicopter is operated at hotter and higher conditions, the engine will, as the margin between absolute mechanical and thermodynamic performance shrinks, still be able to output rated power for some time, while the other engines will start to lose mechanical power (compared to their max rating) the first degree or first foot above sea level and standard temperature. I can't find an open source figure for the PT6T-9's increased performance over the Griffon's PT6T-3DE, but suffice to say, if so equipped (with PT6T-9 engines) a Griffon would be able to operate at it's maximum power-related operating limits at higher altitudes and hotter temperatures than it does currently. Again, Vne is an aircraft design limitation that includes many more factors than just available power, so Vne would not be increased, unless something else were significantly changed with components including, but not limited to the rotor system and the flight control system.
In summary, the SkiesMag writer didn't explicitly say the engines would make the Griffon fly faster, but it certainly in writing juxtaposed the two concepts, and it could have been more clearly written. That said, I know the folks at SkiesMag, and I don't think it was a deliberate implication to tie the two ideas together, perhaps rather a limitation on the number of words for the article to get into the level of detail I noted above.
Regards
G2G
