Tuesday, September 30, 2014

OYSN RW18 One Engine Out Missed Approach

A few days ago, one of this blog follower asked me some questions on an one engine out missed approach. He gave an example of missed approach procedure of Sanaa Intl. airport ILS RW18. The chart is shown below. 


I will simulate this missed approach procedure with one engine out in WinPEP using A320-231 aircraft. Calculation type is from any point in flight. The initial conditions and its screenshot are shown below.
  • Air Con: On, Anti Ice: Off
  • Engine level: average, thrust level: idle
  • Configuration: FULL
  • Weight: 66000 kg (MLW)
  • Altitude: 7665 ft (height of 500ft)
  • Speed: 150 KIAS
  • Direction: 179 deg
  • Landing gear: down
  • Engine out: 0

The procedure consists of several flight segments and its first segment screenshoots are shown below:
  1. Landing gear change, thrust rating: go around, engines out: 1
  2. Aero. conf. change: CONF 3
  3. Aero. conf. change: CONF 2
  4. Climb to QNH 8000 ft
  5. Thrust rating: max continuous, acceleration to S speed
  6. Aero. conf. change: CONF 1
  7. Acceleration to Green Dot speed
  8. Climb to QNH 15000 ft

The procedure will start at SAA VOR as missed approach point, then climb to 8000 ft, at D4 SAA right turn to SAA VOR, then intercept R359 SAA to NIBAL waypoint. In this calculation type, the runway tab will be filled by SAA VOR information. This procedure will be tranlated into several ground track steps and its first step screenshot are shown below. 
  1. Fly heading 179 deg, portion end type: Turn to new Navaid SAA at DME 4 SAA, bank angle 20 deg.
  2. Fly direct to Navaid SAA, portion end type: Turn to new Navaid NIBAL at DME 1.7 SAA, bank angle -15 deg.
  3. Fly direct to Navaid NIBAL, portion end type: at Navaid.

Note: we need to key in coordinates of SAA and NIBAL in Navaids definition as shown in screenshoot below.


The WinPEP result is shown below. The altitude of 8000 ft is reached at point DME 4 SAA as shown in the second picture.



I used the result from WinPEP to be analyzed in my EOSID applicaiton inside MATLAB. The resulted 2D and 3D view of terrain and flight procedure are shown below.


The significant terrains along the procedure is shown in graph and table below after considering the loss of gradient during a turn. The most significat terrain is the one around distance of 3.2 km with climb gradient of 0.75%. Since the most significant terrain is below 2.5% climb gradient, this missed approach procedure does not required a special one engine out procedure.



The visualization of this procedure can be viewed in Google earth by downloading this kml files (you can use the same aircrat model as in SLTJ EOSID sample). Some screenshots of flight are shown below. The green circles are flight path markers. 





If you have feedback or something to discuss, please do not hesitate to contact me by email

--o0o--



Thursday, September 25, 2014

One Engine Out Missed Approaches Design

I Introduction 

Generally  any  multi-engine  aircraft  IFR  capable,  flying  under  IMC conditions with  all engine performance can meet gradient capabilities published in missed approaches.  Missed  approach procedures  are  generally  divided  into  the  initial,  intermediate  and  the  final  phase. Obstacle clearance  requirements  begin  in  the  intermediate  phase  with  a  30  metre  (98  feet)  clearance requirement.  In  the  final  phase,  the  obstacle  clearance  requirement  becomes  50  metres  (164 feet).  The nominal climb gradient of a missed approach surface is 2.5%, however higher gradients may be required where obstacle clearance dictates. For older aircraft, particularly piston engined, aircraft compliance with the published missed approach may not  be  achievable  when  operating  at or  near  the  maximum  certificated  weight,  high  altitudes,  high temperatures and engine out conditions.  


Note:    It is the responsibility of the operator to ensure that the aircraft does not conduct an approach at a weight and/or temperature that would not permit the aircraft to comply with the published missed approach procedure under normal “all engine” operational conditions. However under “engine out” emergency  conditions  compliance  with  the  published  missed  approach  procedures  are  not required. 

II  Regulatory Requirements 

For aircraft operating above 5700 kg and in accordance with CASA CAO 20.7.1B, operators must comply with  paragraph  14  of  the  order  for  the  development  of  takeoff  performance  data  and procedures.  Sub-paragraph 14.2, states: 

“ Procedures to be followed consistent with this Order, including procedures anticipating engine failure at any time between the commencement of take-off and completion of landing, must be specified in the Operator’s Operation Manual. The procedures so specified must be such that they can be consistently executed in service by flight crews of average skill and they must also be  such  that the  take-off  flight  path  with  all  engines  operating  is  above  the  one-engine inoperative take-off flight path.” 

As  stated  above,  procedures  anticipating  engine  failure  at  any  time between  the commencement of takeoff and completion of landing must be specified. This includes missed approaches with an engine out. 

More specifically CAO 20.7.1B Paragraph 5.1(b) specifies that the landing weight of the aircraft must be reduced  to  meet  amongst  other  things,  the  approach  climb  requirements  in  Paragraph 9.  The  approach climb  performance  requirements  in  Paragraph  9  stipulates  that  a  gross gradient  of  2.1%  for  twin-engine aircraft,  2.3%  for  three  engine aircraft  and 2.4%  for  four engine aircraft  must be  available for  engine  out performance.  This  is  obviously  the  minimum climb  certification  requirement  and  is  not  related  to  any published missed approach procedures. Paragraph 12 makes reference to obstacle clearance however, it is limited to the context of takeoff and enroute. 

III Guidance 

Operators  should  develop  engine  out  missed  approach  guidance  for  all  instrument  approach procedures where  the  aircraft  would  not  be  able  to  comply  with  the  climb  gradient performance  requirements  of  the normal published missed approach procedures with an engine out. 

It  is  the  responsibility  of  the  operator  to  ensure  that,  for  any  engine  out  missed  approach procedures developed  for  use  within  their  operation,  sufficient  aircraft  performance  studies have been  developed  to verify that the procedure provides adequate obstacle clearance throughout the flight path. When developing engine out missed approach procedures, operators may be limited to flight paths that would only allow for obstacle avoidance until sufficient altitude is achieved to land at the airport or fly to an alternate airport as required by the type of emergency.

The intent is to identify the best option or options for a safe lateral ground track and flight path to follow in the  event  that  a  missed  approach  or  balked  landing  go-around  is  necessary  with  an engine  out.  To accomplish  this,  the  operator  may  develop  the  methods  and  criteria  for  the analysis  of  engine-out procedures which best reflect that operator's operational procedures. 

Specific Engine Out Missed Approach Procedures may be designed when compliance with the published missed  approach  procedure  cannot  be  achieved  during  engine  out  operations.  An alternative  option  to designing an engine out missed approach procedure may be, to use an existing EOSID for the nominated runway.  

Note:  If an operator chooses to use an EOSID in lieu of a published missed approach path, they must first demonstrate  that  the  aircraft  has  the  navigational  capability  to  overfly  the  landing threshold,  track runway centreline and overfly the runway end within the initial splay tolerance. Depending upon the operation type, the splay width can vary between 90 and 150 metres. Furthermore, the aircraft system and navigational capability needs to be assessed  to  ensure  that the  aircraft  can  be  flown  to  the  required tolerance in  IMC  and  crew procedures must be in place to adequately address this manoeuvre. 

In the absence of an Engine Out Missed Approach Procedure, the following provides sample methods of ensuring that obstacle clearance is maintained during an engine out missed approach.  
1. Limit the approach climb weight and thus the landing weight such that the aircraft can comply with the published gradient (2.5% and above) at the operating minima with an engine out.  
2. Limit the operating minima to a height where the missed approach equivalent gradient capability is assured at the typical mission landing weight. 


3. In the diagram above, if the aircraft cannot comply with a 7.0% climb gradient engine out, the operator may choose  a  higher  minima  to  enable  a  lower  and  compliable  climb  gradient.  Some published  procedures frequently provide alternate minima to accommodate different aircraft performance. 

IV  Missed Approach Procedure Assessment Considerations 

Operators may accomplish such assessments generically for a particular runway, procedure, aircraft type, and expected performance, and need not perform this assessment for each specific flight. Operators may use  simplifying  assumptions  to  account  for  the  transition,  reconfiguration  and acceleration  distances following go-around (e.g., use expected landing weights, anticipated landing flap settings). 

The  operator  should  use  the  best  available  information  or  methods  from  applicable  aircraft manuals  or supplementary information from aircraft or engine manufacturers. If performance or flight path data are not otherwise available to support the necessary analysis from the above sources, the operator may develop, compute, demonstrate or determine such information to the extent necessary to provide for safe obstacle clearance.  

The operational considerations should include: 

1. Go-around  configuration  transitions  from  approach  to  missed  approach  configuration including expected flap settings and flap retraction procedures. 
2.  Expected speed changes. 
3. Appropriate  engine  failure  and  shutdown  (feathering  if  applicable)  provisions,  if  the approach  was assumed to be initiated with all engines operative. 
4. Any lateral differences of the missed approach flight path from the corresponding takeoff flight path.  
5. Suitable balked landing obstacle clearance, until reaching instrument approach missed approach or 
enroute procedurally protected airspace. 
6. Any performance or gradient loss during turning flight  
7. Methods used for takeoff analysis, engine-out maximum angle climb, or other such techniques.  
8. Operators  may  make  obstacle  clearance  assumptions  similar  to  those  applied  to corresponding takeoff flight paths in the determination of net vertical flight path clearance or lateral track obstacle clearance. 

Source: CAAP 235-4(0), Guidelines for the Consideration and Design of: Engine Out SID (EOSID)  
and Engine Out Missed Approach Procedures, Australian CASA, November 2006.