Ask a helicopter pilot anything

[Siko]

geeks said:

Saw this and thought of this thread...

(deletes thread in massive huff)

[Chuck328]

Siko,

What would (roughly) be your fuel flow ( say at 1000 ft) in the hover compared to cruise speed?

Thanks.

[Siko]

Chuck328 said:

Siko,

What would (roughly) be your fuel flow ( say at 1000 ft) in the hover compared to cruise speed?

Thanks.

I think around 1800 lbs/hr when cruise is circa 1350….so approx 40% more. Flt idle on the ground (rotors turning) still burns approx 600/hr and the APU burns approx 175/he in the air too if you are using it.

[Mercdriver]

I do not have my circular guessing stick from CPL exams any more, like everyone else used as windscreen scraper once exams over.

If I remember aviation fuel has SG of 0.7 so am a correct 1350 lbs per hour is approx 200 gph?


Found online
Take the total weight of the fuel and drop the last zero.
Divide that number in half.
Add those two numbers together! That’s it

So 1350 = 135, half say 70 plus 135 = 200

Much easier than using guessing stick!

Edited by Mercdriver on Thursday 28th April 18:23

[swampy442]

IanH755 said:

The worst/funniest rip-off of someone else's work I'd heard (stolen from various Fast Jets I think) was an awful description of the Merlin (from a seriously cabbagey Groundcrew SNCO) which called it a "Double Rotor Triple Motor Carbon Fibre Troop Provider" (and technically wrong too).

If that wasn't sickening enough, the rumour I'd heard in Afghan which was that someone Aircrew (front end) in Jan '10 at JHF-A had heard that description, was very impressed by it and wanted to use that description below the "Merlin humping a Chinny" wall art before they were fairly swiftly talked out of it.

I was on Merlin for a few years and I never heard anyone call it that. I heard it called many, many other far more derogatory names though

[swampy442]

Siko said:

Lol never heard of that description of a Merlin! I do remember the mural though and have a great picture of it and the name wall from the IRT shack in Al Amarah.

When I was out in Iraq with Merlin, we had the first all female crew with us, and on their first trip someone had drawn a big 'comedy cock' on the 28sqn Lion on the tail. Serious sense of humour failure all round

[swampy442]

Also, Ive got some very interesting pictures of a Merlin that took an RPG round in the side, it didnt go off but passed straight through the cabin! Not to drag the thread off topic

[Quick getaway]

Hello Siko , brilliant thread thanks for starting, absolutely love helicopters, would have loved to have tried this career but due to eyesight requirements never took the plunge. Amazed no ones asked, but in your opinion whats the better helicopter S92 or AW101 ? , they often seemed to be pitted against each other ( looking at Canada in particular SAR birds vs Navy birds etc ).

[JerryEXE]

swampy442 said:

Also, Ive got some very interesting pictures of a Merlin that took an RPG round in the side, it didnt go off but passed straight through the cabin! Not to drag the thread off topic

That was also mentioned earlier in the thread and I’m sure that there are many of us who would like to see those photos.

Excellent thread Siko, one of my favourites.

[Siko]

swampy442 said:

Also, Ive got some very interesting pictures of a Merlin that took an RPG round in the side, it didnt go off but passed straight through the cabin! Not to drag the thread off topic

Feel free to post the picture if you are able - I know exactly the one you mean as I remember it happening. Just please check it’s not restricted or anything first please.

I know the female crew you mean too, all great girls and one of whom was awarded the first Distinguished Flying Cross for a female in RAF history.

[Siko]

Quick getaway said:

Hello Siko , brilliant thread thanks for starting, absolutely love helicopters, would have loved to have tried this career but due to eyesight requirements never took the plunge. Amazed no ones asked, but in your opinion whats the better helicopter S92 or AW101 ? , they often seemed to be pitted against each other ( looking at Canada in particular SAR birds vs Navy birds etc ).

Hi mate, thanks for your comments! It’s a difficult question to answer as it’s like asking what car should I buy to do anything, between a 1990 518d and a 1992 320d?! Merlin has found it’s niche as a SAR platform and seems to be performing well in that role, whereas the smaller lighter, vastly cheaper and more modern S92 has hoovered up commercial operations. I know there are civilian merlins but you are paying a premium for them.

I have only flown the Merlin in a military role and the S92 as a commercial pilot, so comparing apples with pears, but for me the S92 is the simpler, more reliable and the better option.

[loop swing]

Siko said:

Hi mate, thanks for your comments! It’s a difficult question to answer as it’s like asking what car should I buy to do anything, between a 1990 518d and a 1992 320d?! Merlin has found it’s niche as a SAR platform and seems to be performing well in that role,
whereas the smaller lighter, vastly cheaper and more modern S92 has hoovered up commercial operations. I know there are civilian merlins but you are paying a premium for them.

I have only flown the Merlin in a military role and the S92 as a commercial pilot, so comparing apples with pears, but for me the S92 is the simpler, more reliable and the better option.

I'm not sure I've ever seen the 92 referred to as smaller, lighter, cheaper and more modern before

Have you ever had to have a word with a colleague after viewing HFDM data?

[Ityre]

Quick getaway said:
Hello Siko , brilliant thread thanks for starting, absolutely love helicopters, would have loved to have tried this career but due to eyesight requirements never took the plunge. Amazed no ones asked, but in your opinion whats the better helicopter S92 or AW101 ? , they often seemed to be pitted against each other ( looking at Canada in particular SAR birds vs Navy birds etc ).
Hi mate, thanks for your comments! It’s a difficult question to answer as it’s like asking what car should I buy to do anything, between a 1990 518d and a 1992 320d?! Merlin has found it’s niche as a SAR platform and seems to be performing well in that role, whereas the smaller lighter, vastly cheaper and more modern S92 has hoovered up commercial operations. I know there are civilian merlins but you are paying a premium for them.

I have only flown the Merlin in a military role and the S92 as a commercial pilot, so comparing apples with pears, but for me the S92 is the simpler, more reliable and the better option.

Hi Siko, thanks for taking the time to respond, that makes sense, the Merlin does seem complex, three engines equals more complex gearbox etc etc , I read some years ago, 1 hours flying cost £15000 😳 that’s probably now easily £25000 ! No commercial operator would want that.

[Talksteer]

Siko said:

Hi mate, thanks for your comments! It’s a difficult question to answer as it’s like asking what car should I buy to do anything, between a 1990 518d and a 1992 320d?! Merlin has found it’s niche as a SAR platform and seems to be performing well in that role, whereas the smaller lighter, vastly cheaper and more modern S92 has hoovered up commercial operations. I know there are civilian merlins but you are paying a premium for them.

I have only flown the Merlin in a military role and the S92 as a commercial pilot, so comparing apples with pears, but for me the S92 is the simpler, more reliable and the better option.

It's always struck me that the Merlin is incredibly heavy with its dry mass being a very large % of its MTOW. Part of that is that the mass figures are always for the ASW variant but even the troop carrier is:

9000kg empty
15600kg MTOW (which appears to be an upgrade)

Vs Chinook

11,200kg empty
22,500kg MTOW

Vs CH53E

15,600kg empty
33,300kg MTOW

Vs S92

7000kg empty
12600kg MTOW

From that limited data set we can see a trend that larger helicopters have lower dry mass fractions likely due to certain items being of similar mass irrespective of size however the S92 shades the EH101 despite being lighter.

Any idea why the AW101 turned out so bloated?

[Siko]

loop swing said:

I'm not sure I've ever seen the 92 referred to as smaller, lighter, cheaper and more modern before

Have you ever had to have a word with a colleague after viewing HFDM data?

Yeah fair point about the chubby S92 lol! Ref the hfdm a key part of the programme is conducting crew contacts to find out why a particular event has triggered. I’ve been contacted a couple of times over the years and it was always done with tact and understanding by the gatekeepers. I forget what the first one was, but the second one was triggered by groundspeed being higher than airspeed on approach to land offshore. It was a slack wind day so we had flexibility on which direction to land and the copilot was flying, he chose an approach heading that turned out to be slightly downwind, so we got asked to clarify why we were downwind. Brief email explanation about the variable wind and all accepted fine, I think that particular trigger has gone now (or at least been raised a bit).

[Siko]

Talksteer said:

It's always struck me that the Merlin is incredibly heavy with its dry mass being a very large % of its MTOW. Part of that is that the mass figures are always for the ASW variant but even the troop carrier is:

9000kg empty
15600kg MTOW (which appears to be an upgrade)

Vs Chinook

11,200kg empty
22,500kg MTOW

Vs CH53E

15,600kg empty
33,300kg MTOW

Vs S92

7000kg empty
12600kg MTOW

From that limited data set we can see a trend that larger helicopters have lower dry mass fractions likely due to certain items being of similar mass irrespective of size however the S92 shades the EH101 despite being lighter.

Any idea why the AW101 turned out so bloated?

It's a fair criticism of the Merlin and I think comes down to the original design spec for an anti-submarine helicopter designed for hovering over the sea and parked on a ship. Hence you have an extra engine to allow safe hover performance with a failed engine and heavy items of standard equipment such as powered driveshafts (to permit starting engines for tail folding etc without starting the head). Basically a compromised design is why the troop Merlin is so heavy...sadly.

[Mabbs9]

Hi Siko,

I was up the road in Inverness the other day. As we came down the approach there was a helicopter in the hover on the south side. After we landed and disembarked they were still in the hover.

Probably 25mins. Would that be exhausting? I think a coastguard callsign but can only imagine it was training?

Mabbs

[Lost ranger]

Years ago the met police helicopters of the time (Bell 222s?) always seemed to have the undercarriage down when hovering, even hundreds of feet up. Did the wheels come down automatically at slow speed or was there some other reason?

[Madness60]

Lost ranger said:

Years ago the met police helicopters of the time (Bell 222s?) always seemed to have the undercarriage down when hovering, even hundreds of feet up. Did the wheels come down automatically at slow speed or was there some other reason?

Quite a few helicopters with gear that goes up and down will have warnings if you slow down below a set speed with the gear up, so if you're in and out of the hover a lot eg looking for someone then leave the gear down to avoid having to cancel warnings as you slow down.

[Siko]

Mabbs9 said:

Hi Siko,

I was up the road in Inverness the other day. As we came down the approach there was a helicopter in the hover on the south side. After we landed and disembarked they were still in the hover.

Probably 25mins. Would that be exhausting? I think a coastguard callsign but can only imagine it was training?

Mabbs

Hi Mabbs!

It can be very tiring - I once did a 45min solo wet winching sortie in Anglesey harbour (30 mins hovering or so) was really hard work! I also used to fly a surveillance task on the Puma which involved long periods in a very high hover with extra fuel tanks fitted - think the longest I was in a high hover at night was circa 2 hours and yes that was bloody knackering!

Thankfully most modern helicopters (particularly SAR ones like you saw) have hover modes which help to alleviate the job but they don’t always work perfectly…..