Just Helicopters

Mountain Ridge Helicopters Helicopter Flight Training Higher Ground Helicopters Flight Academy Ocean ColoHeliops 702 Helicopters Helicopter Flight Training

Mountain Ridge Helicopters Helicopter Flight Training Higher Ground Helicopters Flight Academy Ocean ColoHeliops 702 Helicopters Helicopter Flight Training

Subject: Can you help solve an argument?
 
You are not authorized to post a reply.

Author Messages
TribesUser is Offline
JH Newbie
JH Newbie
Posts:4

01/17/2012 7:04 AM  
Hello, My Manager and I were sat at work watching a small rescue / ambulance helicopter hover over a large road this morning. The follow conversation followed: Me - "I wonder how much fuel they use per hour?" Him - "It must use more fuel hovering than it does flying forward" Me - "Surely not, it's not as effected by air friction" Him - "I bet you lunch that you're wrong" Me - "Deal" Can you help solve this argument / win me lunch? I appreciate there are a ton of variants and the question makes no mention of specifics, but can you help? Thank you in advance!
jmann71User is Offline
JH Member
JH Member
Posts:15

01/17/2012 11:57 AM  
alright. here's how you win. yes it takes more power(fuel) to hover than to sustain forward flight, BUT because it is EMS they will most likely pull max torque to achieve the highest airspeed possible, burning more fuel/hour. send me a gift card, i want lunch too!
TribesUser is Offline
JH Newbie
JH Newbie
Posts:4

01/17/2012 12:28 PM  
Thanks for your answer!

To be sure, you're saying that it uses more fuel to hover than it does to fly forward? Surely while flying forward the helicopter is having to counter gravity, wind and air friction; whereas while hovering the helicopter is only countering gravity and wind? Therefore more fuel is used while flying forwards than when hovering.

I appreciate your help.
skipperUser is Offline
JH - Addicted!
JH - Addicted!
Posts:155

01/17/2012 12:38 PM  
Hover power is climb power. Cruise power is less. Hovering uses more fuel per hour than cruising.
iMac__User is Offline
JH - Addicted!
JH - Addicted!
Posts:154


01/17/2012 3:06 PM  
Posted By Tribes on 01/17/2012 7:04 AM
Hello, My Manager and I were sat at work watching a small rescue / ambulance helicopter hover over a large road this morning. The follow conversation followed: Me - "I wonder how much fuel they use per hour?" Him - "It must use more fuel hovering than it does flying forward" Me - "Surely not, it's not as effected by air friction" Him - "I bet you lunch that you're wrong" Me - "Deal" Can you help solve this argument / win me lunch? I appreciate there are a ton of variants and the question makes no mention of specifics, but can you help? Thank you in advance!

With other variables held constant, the rate of fuel consumption is directly proportional to power being developed which is normally equal to the “Power Required”. There’s a power required, airspeed, fuel flow relationship. You can see that relationship from the figure below. Parasite drag accounts for the "air friction" he's talking about, but don’t forget about induced drag.

While hovering induced drag is high, power required is high, and fuel flow is high. As the helicopter moves into forward flight and airspeed increases, the rotor system starts to work on larger volumes of air per-second and the induced drag, power required, and fuel flow decrease.

Moving passed the normal cruse airspeed (high speed range) parasite drag overtakes induced drag and the power required and fuel flow start increasing exponentially.








Regards,
Chris




TribesUser is Offline
JH Newbie
JH Newbie
Posts:4

01/17/2012 3:21 PM  
iMac, Thanks for your concise reply. From what you've said can I put it in a way that my tiny little mind can understand?: Hovering = High fuel consumption Low speed forward flight = Low fuel consumption High speed forward flight = High fuel consumption There is a sweet spot at which low speed flight uses less fuel than hovering. Much appreciated.
iMac__User is Offline
JH - Addicted!
JH - Addicted!
Posts:154


01/17/2012 3:56 PM  
Posted By Tribes on 01/17/2012 3:21 PM
iMac, Thanks for your concise reply. From what you've said can I put it in a way that my tiny little mind can understand?: Hovering = High fuel consumption Low speed forward flight = Low fuel consumption High speed forward flight = High fuel consumption There is a sweet spot at which low speed flight uses less fuel than hovering. Much appreciated.

Generally,

Hovering & Airspeed below 15kts = High fuel consumption

Airspeed above 15kts - Cruse = Lower fuel consumption

Flight around the bucket (60kts - 70kts) = Lowest fuel consumption

High speed flight = High fuel consumption

Regards,
Chris




TribesUser is Offline
JH Newbie
JH Newbie
Posts:4

01/17/2012 6:55 PM  
Thank you for your help guys.

Much appreciated.
boatpixUser is Offline
JH Master Guru
JH Master Guru
Posts:126

02/09/2012 11:56 PM  
This might also help.   In our Robinson R22's the most fuel efficient cruise speed is 83 knots.   The speed at which we stay airborne the longest is 53 knots.  So, if you go out to an oil rig and it blows up you want to try to return at 83 knots to someplace or hover around at 53 knots waiting for the rig to burn out.   Our solo topspeed is 102 knots and that would be a fast cruise.   You might use more power at hover than you would at any of these speeds.  Medivac would by fast cruise to get the patient to the hospital.  In our photo flights the helicopter is usually heavy with two guys onboard but our manuevers are near the 53 knot average.   If you are going faster or slower than 53 knots optimal fuel sipping speed you burn more fuel.  Perhaps a hovercraft is the only other "vehicle" the uses more fuel to go slower.  
You are not authorized to post a reply.
Forums > JH Alternate Forum > General Helicopter Discussion > Can you help solve an argument?



ActiveForums 3.7

Thousands of helicopter professionals from 160+ countries "worldwide" visit JustHelicopters.com every day, making it the Helicopter Industry's #1 Online Resource! Whether a Helicopter Pilot, Helicopter Student, Helicopter Mechanic, Employer, Helicopter Flight School, Helicopter Business, or an enthusiast, JustHelicopters.com has something for you.


© Copyright 2000–2012 Justhelicopters.com

Terms Of Use

Sign In

JustHelicopters.com

Password Assistance

Enter your account user name and click "Send Email".
A temporary password reset link will be emailed to you.

JustHelicopters.com User Registration

Your registration may be used to sign in to these sites:
JustHelicopters.com, VerticalReference.com and JustHelicopters.tv