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Search: Posts Made By: AMDEC
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Forum: Rotorheads
29th Jun 2022, 16:27
Replies: 74
Views: 13,765
Posted By AMDEC

I fully agree Rotorbee and a tail rotor that...

I fully agree Rotorbee and a tail rotor that would lose effectiveness at any time should neither pass.
The spinning of the Cabri is not stopped either because there is a failure or because the pilot...
Forum: Rotorheads
29th Jun 2022, 09:21
Replies: 74
Views: 13,765
Posted By AMDEC

In the certification process you have to claim...

In the certification process you have to claim for a flight envelope (in our case wind envelope) and you have to demonstrate the maneuverability (pedal margin) in that wind envelope. If your tail...
Forum: Rotorheads
29th Jun 2022, 08:45
Replies: 74
Views: 13,765
Posted By AMDEC

But loss of effectiveness does not exist. There...

But loss of effectiveness does not exist. There is no unanticipated yaw you are unable to correct as long as you keep your RPM. LTE was only used as a synonym of unanticipated yaw (#45)
...
Forum: Rotorheads
29th Jun 2022, 07:53
Replies: 74
Views: 13,765
Posted By AMDEC

LTE is not the explanation of unanticipated yaw,...

LTE is not the explanation of unanticipated yaw, it is unanticipated yaw. Unanticipated yaw exists on any single rotor helicopter, even NOTAR helicopters (see the MD902 Grossglockner accident) and...
Forum: Rotorheads
28th Jun 2022, 17:01
Replies: 74
Views: 13,765
Posted By AMDEC

LTE

LTE was used by US Army to designate unanticipated yaw, when they had the problem in the 80's, mainly on OH-58. Bell already noticed in a Service Letter dated July 1984 that the term was misleading....
Forum: Rotorheads
14th Feb 2020, 08:38
Replies: 48
Views: 19,283
Posted By AMDEC

Leprechaun

Accidents occurred on US Army OH58 helicopters. The phenomenon was initially called "Tail rotor stall" and the pilot was asked to add pedal in the turn direction to "unstall" the tail rotor. I am...
Forum: Rotorheads
13th Feb 2020, 10:23
Replies: 48
Views: 19,283
Posted By AMDEC

I would say it is included, even if not...

I would say it is included, even if not explicitely. The pedal curve gives the amount of pedal that is necessary to zero the yawing moment. The fin contribution is therefore included and may lead to...
Forum: Rotorheads
12th Feb 2020, 09:02
Replies: 48
Views: 19,283
Posted By AMDEC

Unanticipated yaw

The EC130 fenestron is derived from the EC135 one by symmetry. Aerodynamically it should behave similarly...

If you are interested in the unanticipated yaw topic and if you have time to spend the...
Forum: Rotorheads
17th Jun 2019, 11:43
Replies: 1,615
Views: 1,869,587
Posted By AMDEC

Losses of yaw control on helicopters

I fully agree that the number of accidents should be related to the number of flight hours. I was not able to find the information.

I do not say that the helicopters that have the largest number...
Forum: Rotorheads
17th Jun 2019, 07:16
Replies: 1,615
Views: 1,869,587
Posted By AMDEC

Losses of yaw control on helicopters

The reproach that can be made about the article in "Pilot" is not what is said of the Cabri, but that it is presented as a problem of the Cabri only. A small look in accident reports databases.(and...
Forum: Rotorheads
26th Apr 2019, 10:50
Replies: 1,615
Views: 1,869,587
Posted By AMDEC

Loss of control in yaw is not specific to the...

Loss of control in yaw is not specific to the fenestron. I looked into accident reports coming from different Aviation Investigation Boards. Between 2010 and 2016 (seven years) I have 9 on the Cabri,...
Forum: Rotorheads
24th Apr 2019, 10:35
Replies: 1,615
Views: 1,869,587
Posted By AMDEC

Fenestron Stall

The Fenestron Stall problem is in the name. The British Army thought that the fenestron stalled and asked to add pedal into the turn when unanticipated yaw started. It can be found in the CAA paper...
Forum: Rotorheads
30th Nov 2018, 12:36
Replies: 1,254
Views: 706,828
Posted By AMDEC

...with no advanced warning, he felt the nose of...

...with no advanced warning, he felt the nose of the helicopter drift right. He initially corrected with left pedal; however, the nose continued to drift right.

This is very similar to what AAIB...
Forum: Rotorheads
30th Nov 2018, 05:11
Replies: 1,254
Views: 706,828
Posted By AMDEC

Failure ?

Unless I missed something the AAIB report does not tell that a failure occurred...
Forum: Rotorheads
10th Nov 2018, 14:57
Replies: 1,254
Views: 706,828
Posted By AMDEC

Why look for a TR failure ?

Statistically there are many more accidents due to unanticipated yaw -- so poorly named as LTE -- than due to TR failures. Looking at the initial yaw, there is no abrupt acceleration. If it is a TR...
Forum: Rotorheads
18th Sep 2018, 10:07
Replies: 38
Views: 7,987
Posted By AMDEC

Vibration issue

Do not think about it. It would be a perfect shaker.
The flapping motion of the blade induces some vertical force at the flapping hinge that directly varies with the flapping angle. If you sum the...
Forum: Rotorheads
17th Feb 2014, 07:39
Replies: 40
Views: 23,282
Posted By AMDEC

Cat A vs Class 1

Cat A and Cat B are defined in certification rules.
Class 1, 2 and 3 are defined in operational rules.

Class 1 and Class 2 performance require the helicopter to be certified in Cat A (and...
Forum: Rotorheads
7th Feb 2014, 07:42
Replies: 13
Views: 2,310
Posted By AMDEC

Simple formula

Try this

n = 0.2 ρ b ℓ R UČ / Mg

where
· ρ is the air density in kg/m3 (1.225 in ISA SL conditions)
· b is the number of blades of the main rotor
· ℓ is the average chord in meters
· R is...
Forum: Rotorheads
5th Aug 2013, 09:01
Replies: 38
Views: 6,215
Posted By AMDEC

The ball is a sideslip indicator on a symmetrical aircraft only

In the helicopter axes (where the ball is actually installed) aerodynamic forces are balanced by inertia forces. The ball only sees inertia forces, but they are a view of the opposing aerodynamic...
Forum: Rotorheads
13th Apr 2013, 20:41
Replies: 1,887
Views: 1,114,378
Posted By AMDEC

Taxi rollover

Not counterbalancing the tail rotor thrust by some main rotor moment can lead to taxi rollover. This has nothing to do with dynamic rollover which occurs in flight when the landing gear hits the...
Forum: Rotorheads
29th Sep 2011, 19:08
Replies: 41
Views: 10,517
Posted By AMDEC

Froude theory (cont)

220 lb asks for 2.2kW. It is only the minimum power required to produce the momentum and lift that weight (assuming 100% efficiency). The drag of the blades and the antitorque are additional power....
Forum: Rotorheads
29th Sep 2011, 07:06
Replies: 41
Views: 10,517
Posted By AMDEC

Froude theory

Froude theory tells that with a 10m diameter rotor you need at least 7.5kW to hover 500lb and more than 12kW for 700lb. The burden is less on the second crew member but still challenging !
Forum: Rotorheads
28th Mar 2011, 11:52
Replies: 12
Views: 5,603
Posted By AMDEC

Increasing the airspeed on a fixed-wing aircraft...

Increasing the airspeed on a fixed-wing aircraft allows to reach higher load factors, sometimes beyond the structural strength. This is why some fixed-wing aircrafts have g-limitations.
There is...
Showing results 1 to 23 of 23


 
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